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The Dyeing of Woollen Fabrics
by Franklin Beech
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Transcriber's note:

Obvious printer's errors have been corrected, and the original spelling has been retained.

Page numbers have been included to allow the reader to use the index. Page numbers of pages previously only containing illustration (and now empty) are not shown.

Illustrations placed in the middle of paragraphes have been moved, thus, their page numbers have changed. The illustration index has been corrected to match the new position of the illustrations.

In chemical formulas a subscripted number is shown by an underscore followed by the number within curly brackets. Thus the formula for water is given as H_{2}O.

Text enclosed by pound signs (#) was in bold face.

Additional notes are at the end of the text.



THE DYEING OF WOOLLEN FABRICS

by

FRANKLIN BEECH Practical Colourist and Chemist; Author of "The Dyeing of Cotton Fabrics," Etc,

With Thirty-Three Illustrations



London Scott, Greenwood & Son 8 Broadway, Ludgate Hill, E.C.

Canada: The Copp Clark Co., Ltd., Toronto United States: D. Van Nostrand Co., New York 1902 [All rights remain with Scott, Greenwood & Son.]



PREFACE. (p. iii)

In this little book the author has endeavoured to supply the dyer of woollen fabrics with a conveniently arranged handbook dealing with the various branches of the wool dyeing industry, and trusts that it will be found to meet the want which undoubtedly exists for such a book.

The text on which the book is based is expressed in the title "The Dyeing of Woollen Fabrics," and in enlarging upon it the author has endeavoured to describe clearly and in some detail the various processes and operations generally, pointing out the principles involved and illustrating these by numerous recipes, showing the applications of a great variety of dyes in the production of the one thousand and one tints and shades the wool dyer is called upon to produce on the fabrics with which he is working. In pursuance of this plan nothing is said of the composition and properties of the various dyes, mordants, chemicals, etc., which are used. This is information every wool dyer should possess, but the author believes it is better dealt with in books devoted to Chemistry proper.

May, 1902.



CONTENTS. (p. v)

CHAPTER I. Page THE WOOL FIBRE— Structure, Composition and Properties...................... 1

CHAPTER II.

PROCESSES PREPARATORY TO DYEING— Scouring and Bleaching of Wool............................ 15

CHAPTER III.

DYEING MACHINERY AND DYEING MANIPULATIONS— Loose Wool Dyeing, Yarn Dyeing and Piece Dyeing Machinery................................................. 40

CHAPTER IV.

THE PRINCIPLES AND PRACTICE OF WOOL DYEING— Properties of Wool — Methods of Wool Dyeing — Groups of Dyes —Dyeing with the Direct Dyes — Dyeing with Basic Dyes — Dyeing with Acid Dyes — Dyeing with Mordant Dyes — Level Dyeing — Blacks on Wool — Reds on Wool — Mordanting of Wool — Orange Shades on Wool — Yellow Shades on Wool — Green Shades on Wool — Blue Shades on Wool — Violet Shades on Wool — Brown Shades on Wool — Mode Colours on Wool.................... 59

CHAPTER V.

DYEING UNION (MIXED COTTON AND WOOL) FABRICS............... 168

CHAPTER VI.

DYEING OF GLORIA........................................... 188

CHAPTER VII. (p. vi)

OPERATIONS FOLLOWING DYEING— Washing—Soaping—Drying................................. 197

CHAPTER VIII.

EXPERIMENTAL DYEING AND COMPARATIVE DYE TESTING............ 211

CHAPTER IX.

TESTING OF THE COLOUR OF DYED FABRICS...................... 218

INDEX...................................................... 225



LIST OF ILLUSTRATIONS. (p. vii)

Fig. Page

1. Microscopical Sketch of Wool Fibre....................... 2

2. Kempy Wool Fibres........................................ 3

3. Sectional View of Wool Fibre............................. 4

4. Wool Fibres Showing Action of Alkalies.................. 10

5. Wool Fibres Showing Action of Acids..................... 11

6. Wool Washing Machine.................................... 20

7. Wool Cloth Washing Machine.............................. 28

8. Woollen Cloth Washing Machine........................... 29

9. Sulphur Bleach House.................................... 29

10. Dyeing Tubs and Vat..................................... 41

11. Section of Dye Vat...................................... 42

12. Delahunty's Dyeing Machine.............................. 44

13. Obermaier Dyeing Machine................................ 44

14. Holliday's Yarn Dyeing Machine.......................... 47

15. Klauder-Weldon Yarn Dyeing Machine...................... 47

16. Dyeing Jiggers for Cloth................................ 51

17. Dyeing Jiggers for Cloth................................ 53

18. Jig Winch Dyeing Machine................................ 53

19. Cloth Dyeing Machine.................................... 54

20. Plush Fabric Dyeing Machine............................. 55

21. Dye Beck for Cloth...................................... 56

22. Hawking Machine......................................... 57

23. Indigo Dye Vat for Cloth............................... 149

24. Squeezing Rollers...................................... 199

25. Yarn Washing Machine................................... 201

26. Cloth Washing Machine.................................. 202 (p. viii)

27. Cloth Washing Machine.................................. 204

28. Soaping and Washing Machine............................ 205

29. Hydro-extractor........................................ 206

30. Hydro-extractor........................................ 207

31. Yarn Drying Apparatus.................................. 208

32. Cloth Drying Machine................................... 208

33. Experimental Dye Apparatus............................. 212



CHAPTER I. (p. 001)

THE WOOL FIBRE.

Wool is one of the most important textile fibres used in the manufacture of woven fabrics of all kinds. It belongs to the group of animal fibres of which three kinds are met with in nature, and used in the manufacture of textile fibres; two of these are derived from quadruped animals, such as the sheep, goat, etc., while the third class comprises the products of certain insects, e.g., silk.

The skin of all animals is covered with more or less of a fibrous coat, which serves as a sort of protecting coat from the weather to the skin underneath. Two different kinds of fibres are found on animals; one is a stiff kind of fibre varying in length very much and called hairy fibres, these sometimes grow to a great length. The other class of animal fibres are the woolly fibres, short, elastic and soft; they are the most esteemed for the manufacture of textile fabrics, it is only when the hairy fibres are long that they are serviceable for this particular purpose. There is a slight difference in the structure of the two kinds of fibre, woolly fibres having a more scaly structure than hairy fibres; the latter also differ in being more cylindrical in form.

Wool.—By far the most important of the animal fibres is wool, the fibre of the domestic sheep. Other animals, the llama or alpaca, the Angora and Cashmere goats also yield fibres of a similar character, which are imported under the name of wools. There are many (p. 002) varieties of wools Which are yielded by the various breeds of sheep, but they may be roughly divided into two kinds, according to the length of "staple," as it is called. In the long-stapled wools the fibres average from 7-1/2 to 9-1/2 inches in length, while the short-stapled wools vary from 1 to 2 inches long. The diameter varies very considerably from 0.00033 to 0.0018 of an inch.



Two varieties of thread are spun from wool, one is known as "worsted," the other as "woollen" yarns; from these yarns two kinds of cloths are woven, distinguished as worsted and woollen cloths; the former are in general not subjected to any milling or felting process, while the latter invariably are.

Physical Properties.—When seen under the microscope the wool fibres show a rod-like structure covered with broad scales, the edges of which project from the body of the fibre, and all point in one direction.

Fig. 1 shows typical wool fibres as viewed under the microscope; the sketch shows very well the scales.

The shape of the scales varies in different breeds of wool. The (p. 003) outer scales enclose inner medullary cells, which often contain pigment matter. A transversed section of the wool fibre shows the presence of a large number of cells. Sometimes wool fibres are occasionally met with which have a peculiar white horny appearance; these do not felt or dye well. They are known as "kempy" fibres. See figure 2. The microscope shows that they are largely devoid of structure, and are formed of very horny, impenetrable tissue, which is difficult to treat in the milling or dyeing process.



The curly or twisted character of the fibre is caused by the unequal contraction of the outer scales, and depends in a great measure upon the hygroscopic nature of the wool. It may be entirely removed for the time by wetting the wool in hot water, then drying it in a stretched condition, or the curl may be artificially induced by unequal drying, a fact which is turned to practical account in the curling of feathers and of hair.

The amount of curl in different varieties of wool is very variable, being as a rule greatest in the finer qualities, and diminishing as the fibre becomes coarser. The diameter of the wool fibre varies (p. 004) from 1/2000 to 1/5000 of an inch, and the number of curls from about 30 per cent. In fine wool as little as 1 or 2 per cent. in the thicker fibres.

Elasticity and strength are properties which, in common with silk, wool possesses in a greater degree than the vegetable fibres. When submitted to strain the wool fibre exhibits a remarkable strength, and when the breaking point is reached the fracture always takes place at the juncture of two rings of the outer scales, the embedded edges of the lower layer being pulled out of their seat. The scales themselves are never broken.



When first formed the cells are more or less of a spherical shape, and contain a nucleus surrounded by the ultimate photoplasmic substance. Those cells which constitute the core or central portion of the fibre retain to some extent this original globular form and pulpy condition. Surrounding this central portion or medulla, as it has been called (see fig. 3), and forming the main bulk of the fibre, there is a comparatively thick layer of partially flattened cells, which are also elongated in the direction of the length of the fibre, and outside this again there is a thinner stratum which may be compared to the bark of a tree. This outer covering differs materially from the (p. 005) rest of the fibre in its physical structure, but is, probably, nearly identical with it, though possibly not entirely so, in chemical composition. It consists of a series of flattened horny scales, each being probably an aggregation of many cells. The scales, which have been compared to the scales of a fish or to slates on a housetop, overlap each other, the free edges protruding more or less from the fibre, while the lower or covered edges are embedded and held in the inner layer of cells. The free edges always point away from the root of the fibre, just as do the bracts of a fir cone.

When viewing a section of a wool fibre there is, of course, no sharp line of division between the three portions above described, but the change from the central spherical cells to the elongated cellular portion, and from these again to the flattened horny scales, is quite gradual, so that the separation into zones, though well marked, is very indefinite in respect of boundaries.

The scaly structure of wool is of great importance in regard to what is known as felting property. When woollen fabrics are worked in boiling water, especially in the presence of soap, they shrink in length and breadth, but become thicker in substance, while there is a greater amalgamation of the fibres of the fabric together to form a more compact and dense cloth; this is due to the scaly structure of the wool fibres enabling them to become entangled and closely united together. In the manufacture of felt hats this is a property of very great value.

Variations in Physical Structure.—Wool fibres vary somewhat amongst themselves; fibres from different breeds of sheep, or even from different parts of the same animal, vary greatly, not only in thickness, length, etc., but also in actual structure. A typical wool fibre, such as may be obtained a good merino or Southdown fleece, will possess the typical structure described above, but frequently the type is departed from to such an extent that the central core of (p. 006) globular cells is entirely absent. Also the serrated character of the outermost layer of cells reaches a much higher state of development in some samples of wool than in others.

Wool is a much more hygroscopic fibre than cotton or any of the other vegetable fibres, usually it contains about 18 per cent. of water, but much depends upon the atmospheric conditions that prevail. This water is contained in the wool in two forms: (1) as water of hydration amounting to about 81 per cent., and (2) as hygroscopic water.

Experiments have shown that when a piece of dried wool is exposed to an atmosphere saturated with water vapour it will absorb 50 per cent. of its weight; cotton under the same conditions will take up 23 per cent.; flax, 27.5 per cent.; jute, 28.5 per cent., and silk, 36.5 per cent.

Heated to about 100 deg. C. it parts with nearly the whole of its water and becomes hard, horny and brittle, exposed to the air, the dry wool again absorbs water and is restored to its former condition. When heated to 100 deg. C. wool becomes somewhat plastic, so that whatever form is then imparted to it it will retain when it becomes cold, this property is very useful in certain processes of finishing wool fabrics, making hats, etc.

Chemical Composition.—In the natural or raw state each wool fibre is surrounded by a considerable amount of foreign matter, so that in treating of its chemical constitution it is necessary to distinguish between pure wool and the raw fibre. The incrusting substance is technically known as "Yolk," or "Suint," and is principally composed of a kind of natural soap, consisting of the potash salts of certain fatty acids, together with some fats which are incapable of saponification.

The amount of yolk present upon different samples of wool varies greatly, the finer varieties containing, as a rule, a larger proportion than the coarser, and less valuable sorts.

The variation in the relative amount of pure fibres and yolk is (p. 007) well shown in the following analyses which, however, do not by any means represent extreme cases.

ANALYSES OF RAW MERINO WOOL. DRIED AT 100 deg. C.

No. 1. No. 2. Moisture 6.26 10.4 Yolk 47.30 27.0 Pure Wool 30.31 59.5 Dirt 11.13 3.1 ——— ——— 100.00 100.00

Yolk consists very largely of two complex substances which have been termed wool perspiration and wool fat. The former is composed of the potash salts of fatty acids, principally oleic and stearic acids; the latter of the neutral carbohydrate, cholesterine, with other similar bodies. The wool perspiration may be removed by a simple washing with water, and on the Continent forms a valuable source of potash salts, since the ash after ignition contains 70 to 90 per cent. of potassium carbonate. The wool fat is insoluble in water, but dissolves readily in ether, benzene, carbon disulphide, etc.

It is also removed from the wool by a treatment with alkali, and it is not easy to explain the action in the case, since the wool fat is not a glyceride, and will not form a soap, but is probably emulsified by the wool perspiration.

Chemical Composition of the Pure Fibre.—The following analyses of purified and dried wool fibre indicate its percentage composition:—

Mulder. Bowman. Carbon 50.5 per cent. 50.8 per cent. Hydrogen 6.8 " 7.2 " Nitrogen 16.8 " 18.5 " Oxygen 20.5 " 21.2 " Sulphur 5.4 " 2.3 " ——- ——- 100.0 100.0

It is sometimes stated that wool fibre consists of a definite (p. 008) substance, keratine, but this view cannot now be admitted, since wool appears to be composed of a mixture or combination of several very complex substances. It is possible and even probable that the outer epidermal scales have a somewhat different composition to the bulk of the fibre, but whether that is the case or not is not known with any degree of certainty, this much can be asserted, that wool is not a simple definite chemical compound.

Sulphur is by far the most variable constituent of wool, sometimes as little as 1.5 and occasionally as much as 5 per cent. being found. It appears to be always present in two different forms, one portion being in very feeble combination and easily removed by alkalies, the remainder, which, according to Knecht, amounts to about 30 per cent. of the total sulphur, cannot be removed without complete disintegration of the fibre. This latter portion does not give a black coloration with plumbite of soda.

The amount of ash left on incinerating dry wool varies from 1 to 2 per cent., and some have considered this inorganic matter as an essential constituent. It consists principally of salts of potassium, calcium and aluminum, with, of course, sulphur.

The chemical composition of the wool fibre is evidently of a most complicated nature; judging from its behaviour in dyeing it is evident that it may contain two bodies, one of a basic character which enables it to combine with the azo and acid series of dyes, the other possessing acid characters enabling it to combine with the basic dyes of the magenta and auramine type. Dr. Knecht has isolated from the wool fibre by extraction with alkalies and precipitation with acids a substance to which the name of lanuginic acid has been given. It is soluble in hot water, precipitates both acid and basic colouring matters in the form of coloured lakes. It yields precipitates with alum, stannous (p. 009) chloride, chrome alum, silver nitrate, iron salts, copper sulphate. It appears to be an albuminoid body. From its behaviour with the dyes, and with tannic acid and metallic salts, it would appear that lanuginic acid contains both acidic and basic groups. It contains all the elements, carbon, hydrogen, oxygen, nitrogen and sulphur, found in wool.

If wool is dyed in a dilute solution of Magenta (hydrochloride of rosaniline), the whole of the base (rosaniline) is taken up, and the whole of the acid (HCl) left in the bath, not, however, in the free state, but probably as NH_{4}Cl, the ammonia being derived from the wool itself. A further proof of the acid nature of lanuginic acid is that wool may be dyed a fine magenta colour in a colourless solution of rosaniline base; for since rosaniline base is colourless, and it only forms a colour when combined with acids, the fibre has evidently acted the part of an acid in the combination.

Chemical Properties. Action of Alkalies.—Alkalies have a powerful action on wool, varying, of course, with the nature of the alkali, strength of solution and temperature at which the action takes place.

An ammoniacal solution of copper hydroxide (Schweizer's reagent), has comparatively little action in the cold, but when hot it dissolves wool fairly readily.

The caustic alkalies; sodium hydroxide, NaOH, or potassium hydroxide KOH, have a most deleterious action on wool. Even when very dilute and used in the cold they act destructively, and leave the fibre with a harsh feel and very tender, they cannot therefore be used for scouring or cleansing wool. Hot solutions, even if weak, have a solvent action on the wool fibre, producing a liquid of a soapy character from which the wool is precipitated out on adding acids.

This action of alkalies has an important bearing on the scouring of wool, for if this operation be not carried out with due care there (p. 010) is in consequence great liability to impair the lustre and strength of this fibre. From microscopical examination this effect of alkalies is seen to be due to the fact that they tend to disintegrate the fibre, loosen and open the scales, this is shown by contrasting the two fibres A and B shown in figure 4, A being a normal wool fibre, B one strongly treated with an alkali.

The alkaline carbonates have but little action on wool, none if used dilute and at temperatures below 120 deg. F.



Soap has practically no action on wool, and is therefore an excellent scouring material for wool. The carbonate of ammonia is the best and has the least action of the alkaline carbonates, those of potash and soda if used too strong or too hot have a tendency to turn the wool yellow, the carbonate of potash leaves the wool softer and more lustrous than the carbonate of soda.

The influence of scouring agents on wool will be discussed in the chapter on cleansing wool fabrics in more detail.

Caustic or quick-lime has a similar injurious action on the wool fibre as the caustic alkalies.

Action of Acids.—Acids when dilute have but little influence on (p. 011) the wool fibre, their tendency is to cause a separation of the scales (see fig. 5) of the wool and so make it feel harsher. Strong acids have a disintegrating action on the wool fibre. There is a very considerable difference between the action of acids on wool and on cotton, and this difference of action is taken advantage of in the woollen industry to separate cotton from wool by the process commonly known as "carbonising," which consists in treating the fabric with a weak solution of hydrochloric acid or some other acid, then drying it; the cotton is disintegrated and falls away in the form of a powder, while the wool is not affected, sulphuric acid is used very largely in dyeing wool with the acid- and azo-colouring matters.



Nitric acid affects wool in a very similar manner to the acids named above when used in a dilute form; if strong it gives a deep yellow colour and acts somewhat destructively on the fibre.

Sulphurous acid (sulphur dioxide) has no effect on the actual fibre, but exercises a bleaching action on the yellow colouring matter which the wool contains, it is therefore largely used for bleaching (p. 012) wool, being applied either in the form of gas or in solution in water; the method will be found described in another chapter. Wool absorbs sulphur dioxide in large amount, and if present is liable to retard any subsequent dyeing processes.

Action of Other Substances.—Chlorine and the hypochlorites have an energetic action on wool, and although they exert a bleaching action they cannot well be used for bleaching wool. Hot solutions bring about a slight oxidation of the fibre, which causes it to have a greater affinity for colouring matters; advantage is taken of this fact in the printing of delaines and woollen fabrics, while the woollen dyer would occasionally find the treatment of service. A paper by Mr. E. Lodge, in the Journal of the Society of Dyers and Colourists, 1892 (p. 41), may be consulted with advantage on this subject. Wool treated with chlorine loses its felting property, and hence becomes unshrinkable, a fact of which advantage is taken in preparing unshrinkable woollen fabrics.

When wool is boiled with solutions of metallic salts, such as the sulphate of iron, chrome, aluminium and copper, the chlorides of tin, copper and iron, the acetates of the same metals, as well as with some other salts, decomposition of the salt occurs and a deposit of the metallic oxide on the wool is obtained with the production of an acid salt which remains in solution. In some cases this action is favourably influenced by the presence of some organic acid or organic salt, as, for examples, oxalic acid and cream of tartar (potassium tartrate), along with the metallic salt.

On this fact depends the process of mordanting wool with potassium bichromate, alum, alumina sulphate, ferrous sulphate, copper sulphate, etc. The exact nature of the action which occurs is not properly understood, but there is reason for thinking that the wool fibre has the capacity of assimilating both the acid and the basic constituents of the salt employed.

Excessive treatment with many metallic salts tends to make the (p. 013) wool harsh to the feel, partly owing to the scales being opened out and partly owing to the feel naturally imparted by the absorbed metallic salt.

The normal salts of the alkaline metals, such as sodium chloride, potassium sulphate, sodium sulphate, etc., have no action whatever on the wool fibre.

Wool has a strong affinity for many colouring matters. For some of the natural colours, turmeric, saffron, anotta, etc., and for the neutral and basic coal-tar colours it has a direct affinity, and will combine with them from their aqueous solutions. Wool is of a very permeable character, so that it is readily penetrated by dye liquors; in the case of wool fabrics much depends, however, upon the amount of felting to which the fabric has been subjected.

If wool be boiled in water for a considerable time it will be observed that it loses much of its beautiful lustre, feels harsher to the touch, and also becomes felted and matted together. This has to be carefully guarded against in all dyeing operations, where the handling or moving of the yarns is apt to produce this unfortunate effect.

After prolonged boiling the fibre shows signs of slight decomposition, from the traces of sulphuretted hydrogen and ammonia gases which it evolves.

When wool is dried at 212 deg. F. it assumes a husky, harsh feel, and its strength is perceptibly impaired. According to Dr. Bowman, the wool fibre really undergoes a slight chemical change at this temperature, which becomes more obvious at 230 deg. F., while at about 260 deg. F. the fibre begins to disintegrate. According to the researches of Persoz, however, temperatures ranging from 260 deg. F. to 380 deg. F. can be employed without any harm to the wool, if it has previously been soaked in a 10 per cent. solution of glycerine.

When wool is heated to 212 deg. F. (100 deg. Cent.) it becomes (p. 014) quite pliant and plastic and may be moulded into almost any shape, which it still retains when cold. This fact is of much interest in the processes of finishing various goods, of embossing velvet where designs are stamped on the woven fabric while hot, and in the crabbing and steaming of woollen goods, making hats, etc.



CHAPTER II. (p. 015)

PROCESSES PREPARATORY TO DYEING, SCOURING AND BLEACHING OF WOOL.

Wool scouring takes place at two stages in the process of manufacture into cloth. First, in the raw state, to free the wool from the large amount of grease and dirt it naturally contains; second, after being manufactured into cloth, it is again scoured to free it from the oil that has been added to the scoured raw wool to enable it to spin easily. This oiling is generally known as wool batching, and before the spun yarns or woven fabrics can be dyed it is necessary to remove it.

Raw wool is a very impure substance, containing comparatively little wool fibre, rarely more than 50 to 60 per cent. in the cleanest fleeces, while it may be as low as 25 per cent. in the dirtiest.

First there is a small quantity of dirt; there is what is called the suint, a kind of soapy matter, which can be removed by washing in hot water. This soap has for its base potash, while its acids are numerous and complex. The wool contains a fatty-like substance of the nature of wax, called cholesterine, and this imparts to the fatty matter, which be extracted from the wool fibre, very peculiar properties. Besides these there are several other bodies of minor importance, all of which have to be removed from the wool before it can be manufactured into cloth.

Marker and Schulz give the following analysis of a good sample of (p. 016) raw wool:—

Moisture 23.48 per cent. Wool fat 7.17 " Wool soap (suint), soluble in water 21.13 " Soluble in alcohol 0.35 " Soluble in ether 0.29 " Soluble in dilute hydrochloric acid 1.45 " Wool fibre 43.20 " Dirt 2.93 " ——— 100.00

Two principles underlie the methods which are in use for this purpose. The first principle and the one on which the oldest method is based is the abstraction of the whole of the grease, etc., from the wool by means of an alkaline or soapy liquor at one operation. This cannot nowadays be considered a scientific method. Although it extracts the grease, etc., from the wool, and leaves the latter in a good condition for after processes, yet with it one might almost say that the whole of the soap or alkali used, as well as the wool grease itself, is lost as a waste product; whereas any good process should aim at obtaining the wool grease for use in some form or another. The second principle which underlies all the most recent methods for extracting the grease from the wool, consists in treating the fibre with some solvent like benzol, carbon bisulphide, petroleum spirit, carbon tetrachloride, etc., which dissolves out the cholesterine and any other free fatty matter which is in the wool fibre, leaving the latter in such a condition that by washing with water the rest of the impurities in the wool can be extracted. By distilling off and recondensing the solvent can be recovered for future use, while the wool fat can also be obtained in a condition to use for various purposes. This is rather a more scientific method than the old one, but it has not as yet come into extensive use.

Wool Scouring. Old Methods.—In the early days of wool scouring (p. 017) this operation was done in a very primitive fashion, generally in a few tubs, which could be heated by steam or otherwise, and in which wool was worked by means of hand forks. These primitive processes are still in use in some small works, especially where the wool is dyed in the loose condition, but in all the large works machinery has been adopted, which machinery has been brought to a high state of perfection, and does its work very well, and without much attendant manual labour.

The alkaline substances used in this process of scouring demand some notice. These comprise soda ash, soda crystals, caustic soda, silicate of soda, potash, caustic potash, soaps of various kinds, stale urine, ammoniacal compounds. Which of these may be used in any particular case depends upon a variety of reasons. Potash is the best alkaline agent to use. It agrees better with the fibre than any other, leaving it soft and elastic. Ammonia is the next best, but it does not take out the grease as well as the potash. Soda does not suit as well as potash, as it has a tendency to leave the fibre harsh in feel and somewhat brittle, yet on account of its being so much cheaper it is the most largely used. The use of silicate of soda cannot be recommended, as it has a great tendency to leave the fibre hard, which may be ascribed to the deposition of silica on the fibre.

The caustic alkalies cannot be used as they have too solvent an action on the fibre. The carbonates, therefore, in the form of soda ash or potash, or pearl ash, are used, or better still, soap is used as it has a greater solvent action on the fatty matter of the wool than have the alkalies, and in this respect a potash soap is better than a soda soap.

The character of the wool determines the alkali to be used; fine, long-stapled wools, which are usually very free from grease in excess, should always be treated with potash, or a potash soap, which will (p. 018) remove the whole of the grease from the wool, leaving the latter in a fine, soft, silky condition.

Short-stapled wools can be treated with soap and a little soda ash, but too much of the latter is to be avoided. Coarse and greasy wools may be scoured with soap and soda ash, or other alkali which is almost necessary to remove the large amount of grease these wools contain.

Practically the only alkaline products now in use are the various hard and soft soaps, and the carbonates of soda and potash in their various forms of soda ash, soda crystals, potashes, pearl ash, etc. Ammonia and its compounds are rarely used, while stale urine, which acts in virtue of the ammonia it contains has practically gone out of use.

Hand-Scouring.—Wool scouring by hand is easily done and requires few appliances, simple tubs or vats of sufficient capacity in which steam pipes are placed, so that the scouring liquors can be heated up. The best temperatures to use are about 130 deg. to 140 deg. F., and it is not advisable to exceed the latter, as there is then some risk that the alkali may act on the fibre too strongly.

The strength of the scouring liquor necessarily varies with the kind of wool being treated, and with the kind of alkaline product used; if soft, fine wools are being treated, then the liquor may be made with 1 to 2 lb. of soap to 10 gallons of water (if a mixture of soap and alkali is used, then it may contain from 1/4 to 1/2 lb. soda ash, and 1/2 lb. to 1 lb. of soap). For coarse, greasy wools these quantities may be increased by about one-half. The best plan of scouring by hand is to treat the wool in a tub with a scouring liquor for about half an hour, then to squeeze out the surplus liquor and to treat again in a new liquor for half an hour; this liquor may be used for a new batch of wool. The wool is often put into nets, and these are lifted up and down in the liquor so as to cause it to penetrate to every part of the wool.

It is not advisable to work the wool about too much, otherwise (p. 019) felting might ensue and this must be avoided. The felting of the wool is one of the troubles of the wool-scourer and is often difficult to avoid, it is mostly brought about by excessive working of the wool during the process, and by the use of too high a temperature in the scouring bath. The remedies are obvious to the practical man, as little handling of the wool as possible, and at as low a temperature as possible. Still it is necessary to see that the scouring liquor penetrates to every part of the wool which is being treated.

To ensure this, care must be taken not to scour too much at one time, so that the wool is loosely placed in the scouring tub, if placed loose in the latter, the workmen can by means of forks work it to and fro while in process of treatment. After the wool has been through these scouring liquors it is thrown on a scray to drain, and is next placed in cisterns which have perforated false bottoms. In these cisterns it is washed with cold water two or three times, the water being run off from the wool between each washing; it is then spread out in a room to dry. As a rule, a man can wash from 500 lb. to 600 lb. of wool in a day by this method. Another plan which is sometimes adopted so as to avoid handling the wool as much as possible, and thus prevent felting, is to place the wool in cages having perforated sides which will hold about 1 cwt. of wool. They are lowered by means of cranes into the washing liquors, and the wool in them is then worked for a quarter of an hour, when the cages and their contents are lifted out and the surplus liquor allowed to drain off. They are then lowered into the next bath, treated or worked in this, again lifted out and dropped into the wash waters.

There is by this plan a saving of handling, and more wool can be got through in the same time, but it requires two men to work it. These hand processes are only in use in small works, having been (p. 020) replaced in all large works by mechanical methods described below.

Machine Scouring.—Wool-scouring machinery has been brought to a high state of perfection by the successive efforts of many inventors, and by their means wool washing has been much simplified and improved. Wool-washing machinery is made by several firms, among whom may be mentioned Messrs. J. & W. McNaught, and John Petrie, Junior, Limited, both of Rochdale.



Fig. 6 shows one form of wool-washing machine. It consists of a long trough which contains the scouring liquor. In this machine the wool enters at the left-hand end, and is seized by a fork or rake and carried forward by it a short distance, then another rake seizes it and carries it further forward to another rake, and this to the last rake of the machine, which draws it out of the machine to a pair of squeezing rollers which press out the surplus liquor, and from these rollers the scoured wool passes to a travelling band for delivery from the machine. Sometimes the wool is not entered into the trough direct, but is put on a travelling apron which opens it and delivers it in a more open form into the trough. The movement of the forks causes some degree of agitation in the scouring liquor which facilitates the penetration of the liquor through the wool, and thus brings about a better scouring.

After the wool has passed through the machine it is taken and run once more through the machine. Some scourers use the same liquor, but it is better to use fresh liquors, after which it is washed in the same machine with water two or three times. With a single machine there is some time and labour lost in transferring the wool from one end to the other between the separate treatments, and in large works where a great deal of wool is scoured it is usual to place three or four of these machines end to end.

The first is filled with strong scouring liquor, the second with (p. 022) a weaker liquor, while the third and fourth contains wash waters, and the wool is gradually passed by the action of the machine through the series without requiring any manual aid. Between each machine it is passed through squeezing rollers as before, and finally emerges thoroughly scoured. A good plan of working in connection with such a series of machines is to have four as above, two washing machines and two soaping machines, the soap liquor is run through these in a continuous stream, entering in at the delivery end of the second soaper and passing out at the entering end of the first soaper. The wool as it first enters the machine comes into contact with rather dirty soap liquor, but this suffices to rid it of a good deal of loose dirt; as it passes along the machine it comes in contact with cleaner and fresher soap liquor, which gradually takes all grease and dirt out of it, and, finally, when it passes out it comes in contact with fresh liquor, which removes out the last traces of dirt and grease. In the same way it passes through the washers, being treated at the last with clean water. By this plan the scouring is better done, while there is some saving of soap liquor and wash water, for of these rather less is required than by the usual system. These are matters of consideration for wool scourers. The wool-washing liquors after using should be stored in tanks to be treated for recovery of the grease which they contain.

The temperature of the scouring liquors should be about 100 deg. F., certainly not more than 120 deg. F., high temperatures are very liable to bring about felting, while tending to increase the harshness of the wool, particularly when soda is the agent used. By this method all the wool fat, suint, etc., of the wool find their way into the soap liquors. These were formerly thrown away, but they are generally treated with acid and the fat of the soap and wool recovered, under the name of wool grease or Yorkshire grease. (Vide G. H. Hurst, (p. 023) "Yorkshire Grease," Jour. Soc. Chem. Ind., February, 1889.)

The wool fat consists largely of a peculiar fat-like body known as cholesterine. This, however, is unsaponifiable, and cannot be made into soap; at the same time when it gets into, as it does, the recovered wool grease it spoils the latter for soap-making purposes.

Cholesterine has some properties which make it valuable for other purposes; it is a stable body not prone to decomposition, it is capable of absorbing a large quantity of water, and it is on these accounts useful for medicinal purposes in the production of ointments, and it might be useful in candle-making. When it gets into recovered grease it cannot be extracted from it in an economical manner. The wool suint consists largely of the potash soaps of oleic and stearic acids. These two fatty acids find their way into the recovered wool grease but the potash salts are lost, while they would be valuable for various purposes if they could be recovered.

Another form of wool-washing machine has a frame carrying a number of forks arranged transversely to the machine. The forks are by suitable gearing given a motion which consists of the following cycle of movements. The forks are driven forwards in the trough of the machine, carrying the wool along with them, they are then lifted out, carried back, and again allowed to drop into the machine, when they are ready to go forward again. Thus the forks continually push the wool from one end of the machine to the other.

It is a common plan to have three machines placed end to end, so that the wool passes from one to the other; in a set of this kind the first machine should have a capacity of 1,500 gallons or thereabouts, the second 1,000 gallons, and the third 750 gallons.

Wool Scouring by Solvents.—Of late years processes have been (p. 024) invented for the scouring of wool, either raw or spun by means of solvents, like carbon bisulphide, benzol, petroleum spirit, etc. Such processes are in a sense rather more scientific than the alkali processes, for whereas in the latter the grease, etc., of the wool and the oil used in batching it are practically lost for further use, and therefore wasted, being thrown away very often, although they may be partially recovered from the used scouring liquors, in the solvent processes the grease and oil may be recovered for future use for some purpose or other.

The great objection to these processes is the danger that attends their use, owing to the inflammable character of the solvents. Several other objections may be raised, some of which are mechanical, and due to the want of proper machinery for carrying out the processes. There are many ways in which solvents may be applied, some are the subject of patents. It is not possible to describe the details of all these, but two of the most recent will be mentioned.

In Singer's process, which was described in detail by Mr. Watson Smith some time ago before the Society of Dyers and Colourists, carbon bisulphide is used. The raw wool is placed between two endless bands of wire, and it is carried through a series of troughs containing bisulphide of carbon; during its passage through the troughs the solvent takes out the grease, and loosens the other constituents of the wool. After going through the bisulphide the wool is dried and passed through water which completes the process. The carbon bisulphide that has been used is placed in steam-heated stills, distilled off from the grease, condensed in suitable condensers, and used over again. In this process, with care, there is very little loss of solvent. The grease which is recovered can be used for various purposes, one of which is the manufacture of ointments, pomades, etc. The disadvantages of bisulphide are: (1) It tends after some time (p. 025) to cause the wool to acquire a yellow cast, due to the free sulphur which it contains, and which being left in the wool gradually causes it to turn yellow. By using redistilled bisulphide this defect may be avoided. (2) Another defect is the evil odour of the solvent. This, however, is less with redistilled bisulphide than with the ordinary quality, and with suitable apparatus is not insuperable. (3) Another defect is the volatility and inflammability of carbon bisulphide. On the other hand, bisulphide possesses the very great advantage of being at once heavier than, and insoluble in, water, and it can be, therefore, stored under water very much more safely than can any of the other solvents which are used.

Burnell's machine has two troughs filled with benzoline. In these are arranged a large central roller round which are some smaller rollers. The wool passes round the large roller and is subjected to a number of squeezings in passing the smaller rollers. A current of the benzoline is continually passing through the machine. The whole is enclosed in a hood to avoid loss of solvent as far as possible. After passing through the benzoline trough the wool passes through a similar trough filled with water. Benzoline is better than carbon bisulphide in that there is no tendency on the part of the wool to turn yellow after its use, on the other hand it is more inflammable, and when it does take fire is more dangerous, and being lighter than water is not so readily and safely stored. Another feature is that it is not so completely volatile at steam temperatures, so that a little may be left in the grease and thus tend to deteriorate it. Coal-tar benzol, the quality known as 90's, would be better to use.

The solvent processes are well worth the attention of wool scourers, all that is required for their proper development being the production and use of suitable machinery.

After the raw wool has been scoured it is batched, i.e., it is (p. 026) mixed with a quantity of oil for the purpose of lubricating the wool to enable it more easily to stand the friction to which it is subjected in the subsequent processes of spinning and weaving by giving it greater pliability.

For this purpose various kinds of oil are used. Olive oil is the principal favourite, the variety mostly used being Gallipoli oil. Ground-nut oil is also extensively employed, and is cheaper than olive. Oleic acid a by-product of the candle industry, is extensively used under the name of cloth oil, there is also used oleine, or wool oil, obtained by the distillation of Yorkshire grease.

So far as merely oiling the wool is concerned there is not much to choose between these different oils, olive perhaps works the best and agrees best with the wool. Mineral oils have been and can be used either alone or mixed with the oils above mentioned, and so far as lubricating the wool is concerned do very well and are much cheaper than the fatty oils named above.

The following are some analyses of various oils used as cloth oils which the author has had occasion to analyse.

1. 2. 3. 4. Specific gravity at 60 deg. F. 0.9031 0.9091 0.6909 0.8904 Free fatty acid 55.02 64.42 51.52 68.05 Unsaponifiable oil 34.56 9.95 32.80 9.52 Saponifiable oil 10.32 25.32 15.68 12.43 ——— ——— ——— ——— 100.00 100.00 100.00 100.00

Nos. 1 and 2 are prepared from Yorkshire grease. The unsaponifiable matter in these is purely natural, it will be seen it varies within wide limits. Nos. 3 and 4 are made from the oleic acid of the candle factories, and the unsaponifiable matter is due to their containing mineral oil which has been added to them.

So far as regards the object for which the wool is oiled, the mineral oils will answer almost as well as the fatty oils and with most (p. 027) satisfactory results from an economical point of view, for they are much cheaper. But this is not the only point to be considered. The oil has to be got out of the wool before the latter can be dyed. Now while the fatty oils can be easily removed, by treatment with soap, and they can be recovered along with the fat of the soap, mineral oils cannot be entirely removed from the wool, what remains in will interfere very much with the satisfactory dyeing of the wool, and what is got out finding its way into the covered wool grease, spoils this for soap making and other uses, so that on the whole what is gained in lessened cost of oiling is lost by the increased liability to defects in dyeing and consequently depreciation in value of the wool, and to decrease in value of the recovered grease.

The amount of oil used varies from 7 per cent. with the best wools to 15 per cent. with shoddy wools. The scouring agents generally used are the same as those used in loose wool scouring, namely, carbonate of soda for coarse woollen yarns, soap and soda for medium yarns, and soap and ammonia for fine yarns. Prior to treating the yarns it is best to allow them to steep in hot water at about 170 deg. F. for twenty minutes, then to allow them to cool. The actual scouring is often done in large wooden tubs, across which rods can be put on which to hang the hanks of yarn, and in which are placed steam pipes for heating up the bath. The best temperature to treat the yarn at is about 150 deg. F.; too high a temperature must be avoided, as with increased heat the tendency to felt is materially augmented, and felting must be avoided. The hanks are treated for about twenty minutes in the liquor, and are then wrung out, drained, and again treated in new scouring liquor for the same length of time. After rinsing in cold water they are dried and finished.

When the oiled wool has been spun into yarns, whether worsted or (p. 028) woollen, and passes into the hands of the dyer, it is necessary to remove from it all the oil before any dyeing operations can be satisfactorily carried out. This oil is removed by the use of soap and weak alkaline liquors, using these at about 110 deg. to 120 deg. F. The most common way is to have the liquor in a rectangular wooden tank, and hang the hank of yarn in by sticks resting on the edges of the tank; from time to time the hanks are turned over until all the oil has been washed out, then they are wrung out and passed into a tank of clean water to wash out the soap, after which the yarn is ready for dyeing.

When the yarn is of such a character that it is liable to curl up, shrink and become entangled, it is necessary that it be stretched while it is being treated with the soap liquor; this is effected by a stretching apparatus consisting of two sets of rollers connected together by a screw attachment, so that the distance between the two sets of rollers can be varied. The hanks are hung between each pair of rollers, and can be stretched tightly as may be required.

For pressing out the surplus liquor from the hanks of yarn a pair of squeezing rollers is used.

Scouring Woollen Piece Goods.—Very often before weaving the yarns are not scoured to remove the oil they contain, as the weaving is more conveniently done with oily yarn than with a scoured yarn. Before dyeing the oil must be taken out of the pieces, and this can be conveniently done by scouring in a washing machine such as is shown in figures 7 and 8, using soap and soda liquors as before, and following up with a good rinse with water.



The soap liquors used in scouring yarns and pieces become charged with oil, and they should be kept, and the oil recovered from them together with the fatty matter of the soap, by treatment with sulphuric acid. By subjecting the grease or fatty matter so obtained to a boil with caustic soda soap is obtained which may be again used in scouring (p. 029) wool.



Bleaching Wool.—The wool fibre has to be treated very differently from cotton fibre. It will not stand the action of as powerful bleaching agents, and, consequently, weaker ones must be used. This is a decided disadvantage, for whereas with cotton the colouring matter is effectually destroyed, so that the bleached cotton never regains its original colour, the same is not the case with wool, especially with sulphur-bleached wool, here the colouring matter of the fibre is, as it were, only hidden, and will under certain circumstances return. The two materials chiefly used for bleaching wool are sulphur and peroxide of hydrogen.



Sulphur Bleaching.—Bleaching wool by sulphur is a comparatively (p. 030) simple process. A sulphur house is built, the usual size being 12 feet high by 12 feet broad, and about 17 feet long. Brick is the most suitable material. The house should have well-fitting windows on two sides, and good tight doors at the ends (see fig. 9). Some houses have a (p. 031) small furnace at each corner for burning the sulphur, two of these furnaces are fitted with hoods, so that the sulphur gases can be conveyed to the upper part of the chamber, but a better plan, and one mostly adopted where the chamber is used for bleaching pieces, is to construct a false perforated bottom above the real bottom of the chamber, the sulphur being burnt in the space between the two floors. If yarn is being bleached the hanks are hung on wooden rods or poles in (p. 032) the chamber, while with pieces an arrangement is constructed so that the pieces which are stitched together are passed in a continuous manner through the chamber.

When all is ready the chamber doors are closed, and the furnaces are heated, some sulphur thrown upon them, which burning evolves sulphur dioxide gas, sulphurous acid, and this acting upon the wool bleaches it. The great thing is to cause a thorough circulation of the gas through every part of the chamber, so that the yarn or pieces are entirely exposed in every part to the bleaching action of the gas. This is effected by causing the gas to pass into the chamber at several points, and, seeing that it passes upwards, to the ventilator in the roof of the chamber. Generally speaking, a certain quantity of sulphur depending upon the quantity of goods being treated is placed in the chamber and allowed to burn itself out; the quantity used being about 6 to 8 per cent. of the weight of the goods. After the sulphuring the goods are simply rinsed in water and dried.

Sulphur bleaching is not an effective process, the colouring matter is not actually destroyed, having only entered into a chemical combination with the sulphur dioxide to form a colourless compound, and it only requires that the wool be treated with some material which will destroy this combination to bring the colour back again in all its original strength; washing in weak alkalies or in soap and water will do this. Another defect of the process lies in sulphur being volatilised in the free form, and settling upon the wool causes it to turn yellow, and this yellow colour cannot be got rid of.

The goods must be thoroughly rinsed with water after the bleaching, the object being to rid the wool of traces of sulphuric acid, which it often contains, and which if left in would in time cause the disintegration of the wool.

Sometimes the wool is washed in a little weak ammonia or soda (p. 033) liquor, but this is not advisable, as there is too much tendency for the colour of the wool to come back again, owing to the neutralising of the sulphur dioxide by the alkali.

Instead of using the gas, the sulphur dioxide may be applied in the form of a solution in water. The goods are then simply steeped for some hours in a solution of the gas in water until they are bleached, then they are rinsed in water and dried. In this method it is important that the solution of the gas be freshly made, otherwise it is liable to contain but little sulphurous acid, and plenty of sulphuric acid which has no bleaching properties, but, on the other hand, is liable to lead to damage of the goods if it be not washed out afterwards.

A better method of utilising the bleaching action of sulphur in a liquid form is to prepare a bath of bisulphite of soda, and acidify it with hydrochloric acid, then to enter the wool, stirring well for some time, and allowing it to steep for some hours, next to expose to the air for a while, and rinse as before.

It is better to allow the wool to steep for about an hour in a simple bath of bisulphite, then enter into a weak hydrochloric acid bath for a few hours. The acid liberates sulphur dioxide in a nascent condition, which then exerts a more powerful bleaching action than if it were already free.

Even with liquid bleaching the bleach is not any more perfect than it is with the gas bleaching; the colour is liable to come back again on being washed with soap or alkali, although there is a freedom from the defect of yellow stains being produced.

Goods properly bleached will stand exposure to air for some considerable time, but those imperfectly bleached exhibit a tendency to regain their yellow colour on exposure to air. One fault which is sometimes met with in sulphur bleaching is a want of softness in (p. 034) the wool, the process seeming to render the fibre harsh.

Washing in a little weak soft soap or in weak soda will remedy this and restore the suppleness of the wool; at the same time care must be taken that the alkaline treatment is not too strong, or otherwise the bleaching effect of the sulphur will be neutralised as pointed out above.

Bleaching Wool by Peroxide of Hydrogen.—During recent years there has come into use for bleaching the animal fibres peroxide of hydrogen, or, as the French call it, oxygenated water. This body is a near relation to water, being composed of the same two elements, oxygen and hydrogen; in different proportions in water these elements are combined in the proportion of 1 part of hydrogen to 8 parts of oxygen, while in the peroxide the proportions are 1 of hydrogen to 16 of oxygen. These proportions are by weight, and are expressed by the chemical formulae for water H_{2}O, and for hydrogen peroxide H_{2}O_{2}. Water, as is well known, is a very stable body, and although it can be decomposed, yet it requires some considerable power to effect it. Now the extra quantity of oxygen which may be considered to have been introduced into water to convert it into peroxide has also introduced an element of instability, the extra quantity of oxygen being ever ready to combine with some other body for which it has a greater affinity than for the water. This property can be utilised in the bleaching industry with great advantage, true bleaching being essentially a process of oxidation. The colouring matter of the fibre, which has to be destroyed so that the fibre shall appear white, is best destroyed by oxidation, but the process must not be carried out too strongly, otherwise the oxidation will not be confined to the colouring matter, but will extend to the fibre itself and disintegrate it, with the result that the fibre will become tendered and be rendered useless.

Peroxide of hydrogen is a weak oxidiser, and therefore, although (p. 035) strong enough to destroy the colouring matter of the fibre is not strong enough to decompose the fibre itself. Hydrogen peroxide is sold as a water-white liquid, without any odour or taste. Its strength is measured by the quantity of oxygen which is evolved when one volume of the liquid is treated with potassium permanganate; the most common strength is 10 volume peroxide, but 30 and 40 volume peroxide is made. On keeping it loses its oxygen, so that it is always advisable to use a supply up as quickly as possible.

Articles of all kinds can be bleached by simply placing them in a weak solution of the peroxide, leaving them there for a short time, then taking out and exposing to the air for some time. The best plan of applying peroxide of hydrogen is the following: Prepare the bleaching bath by mixing 1 part of peroxide with 4 parts of water. The strength can be varied; for those goods that only require a very slight bleach the proportions may be 1 to 12, while for dark goods the proportions first given may be used. This bath must be used in either a wooden or earthenware vessel. Metals of all kinds must be avoided, as they lead to a decomposition of the peroxide, and therefore a loss of material. To the bath so prepared just enough ammonia should be added to make it alkaline, a condition that may be ascertained by using a red litmus paper, which must just turn blue. Into the bath so prepared the well-scoured goods are entered and worked well, so that they become thoroughly saturated. They are then lightly wrung and exposed to the air for some hours, but must not be allowed to get dry, because only so long as they are moist is the bleaching going on; if they get dry the goods should be re-entered into the bath and again exposed to the air.

If one treatment is not sufficient the process should be repeated. The peroxide bath is not exhausted, and only requires new material to (p. 036) be added to it in sufficient quantity to enable the goods to be readily and easily worked in the liquor. Any degree of whiteness may be obtained with a sufficient number of workings. No further treatment is necessary. It is found in practice that an alkaline bath gives the best results.

Another plan of preparing the bleaching bath is to prepare a bath with peroxide and water as before, then add to a sufficient quantity of a solution of silicate of soda 4 parts of water to 1 of silicate of soda at 100 deg. Tw., to make the bath alkaline. Into this bath the goods are entered and are then exposed to the air as before, after which they may be passed through a weak bath of sulphurous acid, being next well washed in water and dried.

The advantage of bleaching with peroxide is that, as it leaves only water in the goods as the result of action, there is no danger of their becoming tendered by an after development of acid due to defective washing, as is the case with the sulphur bleach. The goods never alter in colour afterwards, because there is nothing left in that will change colour. Some bleachers add a little magnesia to the bath, but this is not at all necessary.

Bleaching with Peroxide of Soda.—Peroxide of soda has come to the front of late for bleaching wool. With it a stronger bleaching bath can be made, while the product itself is more stable than peroxide of hydrogen, only it is needful to keep it in tightly closed metal vessels, free from any possibility of coming in contact with water or organic matter of any kind, or accidents may happen. In order to bleach 100 lb. of wool, a bath of water is prepared, and to this is added 6 lb. of sulphuric acid and then slowly 4 lb. of peroxide of sodium in small quantities at a time. Make the bath slightly alkaline by adding ammonia. Heat the bath to 150 deg. F., enter the wool and allow to remain five to six hours, then rinse well and dry. If the (p. 037) colour does not come out sufficiently white repeat the process.

THE CHLORINATION OF WOOL.

The employment of chlorine in wool dyeing and wool printing has of late years received an impetus in directions previously little thought of. The addition of a little chlorine to the decoction of logwood has been recommended as increasing the dyeing power of the wool. Treating the wool with chlorine has a material influence in increasing its capacity for taking dye-stuffs, and although but little attention has been paid to this circumstance by wool dyers, yet among wool printers it has come largely into use, and enables them to produce fuller and faster shades than would otherwise be possible.

The method involves the treatment of the wool first with an acid, then with a solution of a hypochlorite. The staple becomes soft and supple and assumes a silky character; in dyeing it shows a greater affinity for the dyes than it did previously. Although not deteriorated in strength, it almost entirely loses its felting properties. On account of this feature the process cannot be adopted for wool which has to be fulled, but it is of service where felting of the goods is to be avoided, for worsteds, underwear, woollen and half woollen hosiery, etc., in which the felting property that occurs on washing is rather objectionable.

By the chloring of the wool the intensity of the shade dyed is increased to such a degree that when dyeing with Acid black, Naphthol black, Naphthol green, Nigrosine, Fast blue, Water blue, and some others dyed in an acid bath, but little more than half the dye used on unchlored wool is required, while with Induline, more even and intense shades are obtained than is otherwise possible.

The operation of chlorination can be done either in one or two (p. 038) baths. The choice depends upon circumstances and the judgment of the dyer. The process by the two-bath method, with subsequent dyeing in the second or separate bath is (for 100 lb. of wool), as follows. The first bath contains, for light cloths, yarn, etc., from 3 to 4 lb. sulphuric acid, 168 deg. Tw., and for heavier cloths and felt, where the penetration and equalisation of the colour is difficult, from 8 lb. to 10 lb. of acid. Generally speaking, a temperature of 170 deg. to 175 deg. F. is sufficient, although for heavy wool and for wool with poor dyeing qualities it is well to use the bath at the boil. The treatment lasts for half an hour, in which time the acid is almost completely absorbed.

The second bath contains a clear solution of 10 lb. bleaching powder, which solution is prepared as follows. Dry bleaching powder of the best quality is stirred in a wooden vat with 70 gallons of water, the mass is allowed to stand, the clear, supernatant liquor is run into the vat and the sediment stirred up and again allowed to settle, the clear liquor being run off as before, and 5 gallons more water is run in. The clear liquors of these three treatments are then mixed together to form the chloring bath. Special care should be taken that no undissolved particles of the bleaching powder should be left in, for if these settle on the wool they result in too great a development of chlorine, which injures the wool.

The goods after being in the acid bath are entered in this chlorine bath at a temperature of 70 deg. F., which is then raised to the boil. If the acid bath has been strong, or been used at the boil, it is perhaps best to rinse the goods before entering into the chlorine bath. The hypochlorous acid disappears so completely from this bath that it may at once be used as the dye-bath, for which purpose it is only necessary to lift the goods, add the required amount of dye-stuff, re-enter the goods and work until the bath is exhausted, which generally happens when acid dyes are used. If a separate dye-bath be preferred, this is (p. 039) made and used as is ordinarily done.

To perform all the operations in one bath the acid bath is made with from 3 to 4 lb. sulphuric acid, and the wool is treated therein for thirty minutes at 170 deg. F., until all the acid has been absorbed. Then the bath is allowed to cool down to 70 deg. or 80 deg. F., the clear bleaching powder solution is added, the goods are re-entered, and the bath is heated to the boil. When all the chlorine has disappeared add the dye-stuff, and dye as directed above.

In printing on wool the chlorination of the wool is a most important preliminary operation. For this purpose the cloth is passed for fifteen minutes at 170 deg. F. through a bath containing 3/4 oz. sulphuric acid per gallon of water. Then it is passed through a cold bath of 3/4 oz. bleaching powder per gallon of water, after which the cloth is rinsed and dried and is then ready for printing.

Another method of chloring the wool is to pass the goods through a bath made with 100 gallons of water, 2 gallons hydrochloric acid and 2 gallons bleaching powder solution of 16 deg. Tw. As some chlorine is given off it is best to use this in a well-ventilated place.



CHAPTER III. (p. 040)

DYEING MACHINERY AND DYEING MANIPULATIONS.

Wool is dyed in a variety of forms, raw, loose wool; partly manufactured fibre in the form of slubbing or sliver; spun fibres or yarns, in hanks or skeins and in warps, and lastly in the form of woven pieces. These different forms necessitate the employment of different forms of machinery and different modes of handling, it is evident to the least unobservant that it would be quite impossible to subject slubbing or sliver to the same treatment as yarn or cloth, otherwise the slubbing would be destroyed and rendered valueless.

In the early days all dyeing was done by hand in the simplest possible contrivances, but during the last quarter of a century there has been a great development in the quantity of dyeing that has been done, and this has really necessitated the application of machinery, for hand work could not possibly cope with the amount of dyeing now done. Consequently there has been devised during the past two decades a great variety of machines for dyeing every description of textile fabrics, some have not been found a practical success for a variety of reasons and have gone out of use, others have been successful and are in use in dye-works.

Hand Dyeing.—Dyeing by hand is carried on in the simplest possible appliances, much depends upon whether the work can be done at the ordinary temperature or at the boil. Figure 10 shows round and oval tubs and a rectangular vat much in use in dye-houses. These are (p. 041) made of wood, but copper dye-vats are also made, these may be used for all kinds of material—loose fibre, yarns or cloth. In the case of loose fibre this is stirred about either with poles or with rakes, care being taken to turn every part over and over and open out the masses of fibre as much as possible in order to avoid matting or clotting together. In the case of yarns or skeins, these are hung on sticks resting on the edges of the tub or vat. These sticks are best made of hickory, but ash or beech or any hard wood that can be worked smooth and which does not swell much when treated with water may be used. The usual method of working is to hang the skein on the stick, spreading it out as much as possible, then immerse the yarn in the liquor, lift it up and down two or three times to fully wet out the yarn, then turn the yarn over on the stick and repeat the dipping processes, then allow to steep in the dye-liquor. This is done with all the batch of yarn that is to be dyed at a time. When all the yarn has been entered into the dye-bath, the first stickful is lifted out, the yarn turned over and re-entered in the dye-liquor; this operation is carried out with all the sticks of yarn until the wool has become dyed of the required depth. In the case of long rectangular vats it is customary for two men, one on each side of the vat, to turn the yarns, each man taking charge of the yarn which is nearest to him.



Woven goods may be dyed in the tub or vat, the pieces being drawn in and out by poles, but the results are not altogether satisfactory, (p. 042) and it is preferable to use machines for dyeing piece goods.



Plain tubs or vats, such as those shown in figure 10, are used for dyeing and otherwise treating goods in the cold, or at a lukewarm heat, when the supply of hot water can be drawn from a separate boiler. When, however, it is necessary to work at the boil, then the vat must be fitted with a steam coil. This is best laid along the bottom in a serpentine form. Above the pipe should be an open lattice-work bottom, which, while it permits the free circulation of boiling water in the vat, prevents the material being dyed from coming in contact with the steam pipe. This is important if uniform shades are to be dyed, for any excessive heating of any portion of the bath leads to stains being produced on the material in that part of the bath. Figure 11 shows a vat fitted with a steam pipe. That portion (p. 043) of the steam pipe which passes down at the end of the vat is in a small compartment boxed off from the main body of the vat, so that no part of the material which is being dyed can come in contact with it. A closed steam coil will, on the whole, give the best results, as then no weakening of the dye-liquor can take place through dilution by the condensation of the steam. Many dye-vats are, however, fitted with perforated, or as they are called, open steam coils, in which case there is, perhaps, better circulation of the liquor in the dye-vat, but as some of the steam must condense there is a little dilution of it.

DYEING MACHINES.

Dye-tubs and vats, such as those described above, have been largely superseded by machines in which the handling or working of the materials being dyed is effected by mechanical means. There have been a large number of dyeing machines invented, some of these have not been found to be very practical, and so they have gone out of use. Space will not admit of a detailed account of every kind of machine, but only of those which are in constant use in dye-works.

Dyeing Loose or Raw Wool and Cotton.—Few machines have been designed for this purpose, and about the only successful one is

Delahunty's Dyeing Machine.—This is illustrated in figure 12. It consists of a drum made of lattice work which can revolve inside an outer wooden casing. The interior of the revolving drum is fitted with hooks or fingers, whose action is to keep the material open. One segment of the drum is made to open so that the loose cotton or wool to be dyed can be inserted. By suitable gearing the drum can be revolved, and the dye-liquor, which is in the lower half of the wooden casing, penetrates through the lattice work of the drum, and dyes (p. 044) the material contained in it. The construction of the machine is well shown in the drawing, while the mode of working is obvious from it and the description just given. The machine is very successful, and well adapted for dyeing loose or raw wool and cotton. The material may be scoured, bleached, dyed or otherwise treated in this machine.



The Obermaier Machine, presently to be described, may also be used for dyeing loose cotton or wool.



Dyeing Slubbing, Sliver or Carded Wool.—It is found in practice that the dyeing of loose wool is not altogether satisfactory, the impurities they naturally contain interfere with the purity of the (p. 045) shade they will take. Then again the dyes and mordants used in dyeing them are found to have some action on the wire of the carding engine through which they are passed; at any rate, a card does not last as long when working dyed wools as when used on undyed cotton or wool fibres. Yet for the production of certain fancy yarns for weaving some special classes of fabrics it is desirable to dye the wool before it is spun into thread. The best plan is undoubtedly to dye the fibre after it has been carded and partly spun into what is known as slubbing, or sliver. All the impurities have been removed, the wool fibres are laid straight, and so it becomes much easier to dye. On the other hand, as it is necessary to keep the sliver or slubbing straight and level, no working about in the dye-liquors can be allowed to take place, and so such must be dyed in specially constructed machines, and one of the best of these is the

Obermaier Dyeing Machine, which is illustrated in figure 13.—In (p. 046) the Obermaier apparatus dye-vat, A, is placed a cage consisting of an inner perforated metal cylinder, C, and an outer perforated metal cylinder, D; between these two is placed the material to be dyed. C is in contact with the suction end of a centrifugal pump, P, the delivery end of which discharges into the dye-vat A. The working of the machine is as follows: the slubbing or sliver is placed in the space between C and D rather tightly, so that it will not move about. Then the inner cage is placed in the dye-vat as shown. The vat is filled with the dye-liquor, which can be heated up by a steam pipe. The pump is set in motion, the dye-liquor is drawn from A to C, and in so doing passes through the material packed in B and dyes it. The circulation of the liquor is carried on as long as experience shows to be necessary. The dye-liquor is run off, hot water is run in to wash the dyed material, and the pump is kept running for some time to ensure thorough rinsing, then the water is run off, and by keeping the pump running and air going through a certain amount of drying can be effected. This machine works very well, and with a little experience constant results can (p. 047) be obtained. The slubbing or sliver may be scoured, bleached, rinsed, dyed, washed, soaped, or otherwise treated without removing it from the machine, which is a most decided advantage.



Yarn Dyeing Machines.—In figure 14 is given an illustration of a machine for dyeing yarn in the hank form, made by Messrs. Read Holliday & Sons, of Huddersfield. The illustration gives a very good idea of the machine. It consists of a wooden dye-vat, which can be heated by steam pipes in the usual way. Extending over the vat are a number of reels or bobbins, these are best made of wood or enamelled iron. These reels are in connection with suitable gearing, so that they can be revolved. There is also an arrangement by means of which the reels can be lifted bodily in and out of the dye-vat for the purpose of taking on and off the hanks of yarn. A reel will hold about 2 lb. of yarn. The working of the machine is simple. The vat is filled with the requisite dye-liquor. The reels which are lifted out of the vat are then charged with the yarn, which has been previously wetted out. They are then set in revolution and dropped into the dye-vat, and kept there until it is seen that the yarn has acquired the desired shade. The reels are lifted out and the hanks removed when the machine is ready for another lot of yarn.

There are several makers of hank-dyeing machines of this type, and as a rule they work very well. The only source of trouble is a slight tendency for the yarn on one reel if hung loosely of becoming entangled with the yarn on other reels. This is to some extent obviated by hanging in the bottom of the hank a roller, which acts as a weight and keeps the yarn stretched and so prevents it flying about.

To some makes of these machines a hank wringer is attached.



Klauder-Weldon Hank-dyeing Machine.—This is illustrated in (p. 048) figure 15, which shows the latest form. It consists of a half-cylindrical dye-vat built of wood. On a central axis is built two discs or rod carriers, which can revolve in the dye-vat, the revolution being given by suitable gearing which is shown at the side of the machine. On the outer edge of the discs are clips for carrying rods on which one end of the hanks of yarn is hung, while the other end is placed on a similar rod carrier near the axle. The revolution of the discs carries the yarn through the dye-liquor contained in the lower semi-cylindrical part of the machine previously alluded to. (p. 049) At a certain point in every revolution of the discs the rods carrying the yarns are turned a little; this causes the yarn to move on the rods, and this motion helps to bring about greater evenness of dyeing. The most modern form of this machine is provided with an arrangement by means of which the whole batch of yarn can be lifted out of the dye-liquor. Arrangements are made by which from time to time fresh quantities of dyes can be added if required to bring up the dyed yarn to any desired shade. This machine works well and gives good results. Beyond the necessary labour in charging and discharging, and a little attention from time to time as the operation proceeds, to see if the dyeing is coming up to shade, the machine requires little attention.

Many other forms of hank-dyeing machine have been devised. There is Corron's, in which an ordinary rectangular dye-vat is used. Round this is a framework which carries a lifting and falling arrangement that travels to and fro along the vat. The hanks of yarn are hung on rods of a special construction designed to open them out in a manner as nearly approaching hand work as is possible. The machine works in this way. The lifting arrangement is at one end of the vat, the hanks are hung on the rods and placed in the vat. Then the lifter is set in motion and moves along the vat; as it does so it lifts up each rod full of yarn, turns it over, opening out the yarn in so doing, then it drops it again in the vat. When it has travelled to the end of the vat it returns, packing up the rods of yarn in so doing, and this motion is kept up until the dyeing is completed. This machine is very ingenious.

A type of machine which has been made by several makers consists of an ordinary rectangular dye-vat surrounded with a framework carrying a number of sets of endless chains, the links of which carry fingers. The hanks of yarn are hung on rods at one end of which is a tooth (p. 050) wheel that when in position fits into a rack on the side of the vat. The action of the machine is this, the hanks are hung on the rods and placed at the entrance end of the vat, by the moving of the chains it is carried along the vat and at the same time revolves, thus turning over the yarn, which hangs in the dye-liquor; when it reaches the opposite end of the vat, the rod full of yarn is lifted out, carried upwards and then towards the other end of the vat when it is again dropped into the dye-vat to go through the same cycle of movements which is continued until the yarn is properly dyed.

Piece Dyeing Machines.—Wherever it is possible it is far more preferable to dye textile fabrics in the form of woven pieces rather than in the yarn from which they are woven. During the process of weaving it is quite impossible to avoid the material getting dirty and somewhat greasy, and the operations of scouring necessary to remove this dirt and grease has an impairing action on the colour if dyed yarns have been used in weaving it. This is avoided when the pieces are woven first and dyed afterwards, and this can always be done when the cloths are dyed in one colour only. Of course when the goods are fancy goods containing several colours they have to be woven from dyed yarns.

The most common form of machine in which pieces are dyed is the jigger, commonly called the jig, this is shown in figure 16. It consists of a dye-vessel made long, sufficiently so to take the piece full width, wide at the top, narrow at the bottom. At the top on each side is placed a large winding roller on which the cloth is wound. At the bottom of the jig is placed a guide roller round which passes the cloth. In some makes of jigs there are two guide rollers at the bottom and one at the top as shown in the illustration, so that the cloth passes several times through the dye-liquor. In working the cloth is first wound on one of the rollers then threaded through the guide (p. 051) rollers and attached to the other winding roller. When this is done dye-liquor is run into the jig, and the gearing set in motion, and the cloth wound from the full on to the empty roller. With the object of keeping the piece tight a heavy press roller is arranged to bear on the cloth on the full roller. When all the cloth has passed from one roller to the other it is said to have been given "one end". The direction of motion is now changed and the cloth sent in the opposite direction through the jig and the piece has now received another "end". This alternation from one roller to the other is continued as long as is deemed necessary, much depending on the depth of colour which is being dyed, some pale shades may only take two or three ends, deeper shades may take more. When dyeing wool with acid colours which are all absorbed from the dye-liquor, or the bath is exhausted, it is a good plan to run the pieces several ends so as to ensure thorough fixation of the dye on the cloth.



It is not advisable in working these jigs to add the whole of the dye to the liquor at the commencement, but only a part of it, then when one end is given another portion of the dye may be added, such (p. 052) portions being always in the form of solution. Adding dyes in powder form inevitably leads to the production of colour specks on the finished goods. The reason for thus adding the dye-stuff in portions is that with some dyes the affinity for the fibre is so great that if all were added at once it would be absorbed before the cloth had been given one end, and, further, the cloth would be very deep at the front end while it would shade off to no colour at the other end. By adding the dye in portions this difficulty is overcome and more level shades are obtained, but it is met with in all cases of jigger dyeing. It is most common in dyeing wool with basic dyes like Magenta, Auramine, (p. 053) Methyl Violet or Brilliant Green, and with acid dyes like Acid Green, Formyl Violets, Azo Scarlet or Acid Yellow.



Some attempts have been made to make jiggers automatic in their reversing action, but they have not been successful owing to the greatly varying conditions of length of pieces, their thickness, etc., which have to be dyed, and it is next to impossible to make all allowances for such varying conditions.



In figure 17 is shown the jig in section, when the working of the machine can be more easily traced.

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