Wool Dyeing. Lecture I.
Influence of the impurities contained in water on the operations of scouring, rinsing, and dyeing.

Practical Magazine 22, 1876

A Course of Lecturers: By George Jarmain.

(Chemistry applied to the Arts, Manufactures, &c.)

The third course of Cantor Lectures for the past Session had for its subject "Wool Dyeing," by Mr. George Jarmain; the first, which was delivered on Monday evening, March 6th, was as follows:

Lecture I.

I have been instructed by the Council of the Society of Arts to give the present course of lectures on "Wool-dyeing," in order that students preparing for examination in this subject may have indicated to them the course of study which it is desirable for them to follow.

During the last twenty years, that is, since Mr. Perkin patented the process for the production of a mauve dye from aniline, in the year 1856, the woollen-dyeing trade has experienced great changes in the modes of performing many of its operations. The introduction of a large number of new dyes, through the discoveries of chemists, has necessitated these changes.

The dyer of the present day has, therefore, been educated to the fact that he owes a considerable number of his most beautiful colours to the chemist; and he has even received lessons in dyeing from him, for Schutzenberger and Lalande have taught the indigo dyer that he can dye a piece of cloth by other processes besides that of the woad vat.

The dyer has, in fact, received so many helps from the hands of the chemist, that it is difficult to understand why he does not more frequently endeavour to make himself acquainted with the principles of the science, which he must see is more competent than any other kind of knowledge to enable him to excel in his art.

Oftentimes, when I see the skill which, with long practice and observation, enables our working dyers to produce the excellent work which they turn out, I feel persuaded that were his practice and observation combined with correct scientific knowledge, the British working dyer need fear no rival which any country could produce. He would do well, however, to take to heart the fact that, however much practice he may have as a dyer, and however close his observation may have been, if he does not use the means to enable him fully to comprehend the nature of the operations which he is performing, he will, in the long run, be outstripped by those who have the good sense to combine theory and knowledge with practice.

On the other hand, the chemist is not always competent to give a satisfactory account of some of the ordinary processes of the dye-house, processes which seem to him but ill-adapted to accomplish the objects which the dyer has in view, but which, nevertheless, the dyer does accomplish.

Such being the case, it is very desirable that the chemist and the dyer should work hand in hand, and thus each in turn benefit the other.


This indispensable article claims our first attention. I may say that the success of the operations performed upon wool in the various processes of scouring, rinsing, bleaching, and dyeing will depend very much upon the character of the water employed. It is, therefore, of prime importance that the quality and suitability of the water for the operations intended to be carried on should be ascertained, before establishing new works or removing others already in operation.

Having had a large number and great variety of waters to examine from time to time, in order that their suitability for woollen manufacturing purposes might be ascertained, I have arrived at the following results, which I may term limits of impurity in water suitable for wool scouring and dyeing. The water must fulfil the following conditions: —

1. It must not exceed 7 degrees of hardness by Clark's soap test, of which it should not lose more than 2 degrees by boiling for an hour, and returning the water evaporated.

2. It must not deposit a brown sediment of oxide of iron when exposed freely to the air for some hours, nor must it give a blue coloration when a few drops of a solution of red prussiate of potash are added to a portion of it.

3. A portion of the water contained in a white glass bottle, to which a few drops of a solution of logwood are added, should be coloured of a sherry colour, which may be compared with a portion of distilled water treated in the same way.

4. The water should be clear, and must not throw up a brown scum of oxide of iron or organic matter when heated up to the oil.

5. Samples of wool or woollen fabric mordanted and dyed with the colours required, should compare well with similar samples mordanted and dyed with distilled water, or any other water known to be good.

A water which fulfils the above conditions is suitable for scouring and for the dyeing of woollen colours. Any considerable departure from these conditions will be attended with unsatisfactory results, unless the water be submitted to some treat ment or purification.

The actual examination of the water is performed in the following manner: —

1. Clark’s Soap Test.

This test gives such abundant and important information to the scourer, dyer, and steam-user, that I venture to repeat such details of it that any intelligent operative may apply it to the examination of the waters in which he is most interested. The following are the apparatus and materials employed: —
One burette divided into 50 cubic centimetres, in 1/5 or 1/10 cubic centimetres, stoppered.
One stand and clamp to hold ditto.
One 100 cubic centimetre measure.
One stoppered bottle, about 16 ounces capacity.
One pint of soap test.
One 16-oz, flask, fitted with a perforated cork, through which passes a glass tube ¼-in, bore, and about 4 feet long.
One 3-in. funnel and filter paper.
One retort stand, with Bunsen burner or spirit lamp.

The soap test should be bought of an operative chemist, for it is somewhat troublesome to make. Directions for preparing it, however, may be found in many of our standard text-books of chemistry. The soap test consists of a solution of soap in dilute methylated spirit, of such a strength that, when shaken up with a definite quantity of the water, it will indicate the amount of soap-destroying materials or hardening matters contained in the water. The operation is performed in this way: —

Measure out 100 cubic centimetres of the water to be tested, and pour it into the clean and empty stoppered bottle.

Fix the burette in the clamp, and pour into it the soap test up to the top mark.

Run out the soap test through the glass stopper of the burette into the bottle containing the water, in small portions at a time, shaking the bottle vigorously after each addition; continue this operation until a full lather is formed on the surface of the water, which remains covered with the lather for five minutes.

When this point has been arrived at, read off the number of cubic centimetres which have been run out of the burette, and look for the degree of hardness in the table furnished by Dr. Clark, and which is here appended: —

Table showing the Degree of Hardness.

Degree of Hardness. Soap test measures. Differences as for the next degree of hardness.

The first column gives the degree of hardness, the second the number of soap test measures, and the third is a useful number for determining the fractional part of the next degree — it is the denominator of a fraction, of which the excess above the number indicating the nearest whole degree is the numerator.

If, as sometimes happens, 32 measures of the soap test are insufficient to produce a lather, 50 cubic centimetres of the water are taken, and 50 cubic centimetres of distilled water added, and the hardness of the mixture is determined, the double of which is the true hardness of the water.

The hardness of the water, as determined above, represents the absolute or total hardness caused by the soap-destroying ingredients contained in it, which may consist of bicarbonate of lime, bicarbonate of magnesia, bicarbonate of iron; sulphate of lime, sulphate of magnesia, sulphate of iron; chloride of calcium, chloride of magnesium; free acids, and acid salts.

The degrees of hardness are determined in terms of carbonate of lime or chalk, each degree representing one grain of carbonate of lime per gallon. If hardening matters other than carbonate of lime are the cause of the hardness, then they are present in the following approximative relative proportions, if the whole hardness be due to these bodies respectively: —

Carbonate of lime100 parts
Carbonate of magnesia84 "
Carbonate of Iron116 "
Sulphate of lime (dry)136 "
Sulphate of magnesia (dry)120 "
Sulphate of iron156 "
Chloride of calcium111 "
Chloride of magnesium95 "

That is to say, 100 lbs. of chalk dissolved in a certain bulk of water will make the water as hard as if it had dissolved in it 84 lbs. of carbonate of magnesia, 116 lbs. of carbonate of iron, and so on with the rest.

When water containing the bicarbonates in solution is boiled they are decomposed, carbonic acid being expelled, and they are converted into insoluble carbonates, which precipitate or form an incrustation on the vessel in which they are boiled.

It is often of great importance to the dyer and steam-user to know how much of the hardness of the water is due to the presence of these bicarbonates.

Proceed in this way: —

Pour 100 cubic centimetres of the water into a clean flask fitted with a cork and a long straight tube. Boil gently for an hour, taking care that little or no steam escapes from the top of the tube; filter back into the measure, making the bulk up to 100 cubic centimetres with distilled water if necessary, then take the hardness with the soap test, with the precautions given above. The hardness thus obtained is due to the presence of bodies other than bicarbonates, and is called its "permanent" hardness, and the loss of hardness by the boiling is due to the removal of bicarbonates; the hardness so lost is called "temporary."

The following example will show how the results of an examination of water by the soap test should be calculated: —
A sample of water took 29.6 cubic centimetres to produce a persistent lather, and after boiling one hour and filtering it took only 7 cubic centimetres.

Therefore —
Total hardness = 28.5 = 14 = Degrees 14 11/18
Total hardness = 1.1 = 11/18 = Degrees 14 11/18
Permanent do. = 5.4 = 2 = Degrees 2 8/11
Permanent do. = 1.6 = 16/22 = Degrees 2 8/11
Temporary do. The difference or loss. = - = Degrees 12 nearly.

2. — Examination for Iron Compounds.

These form a very objectionable impurity; for many colours cannot be dyed satisfactorily if iron be contained in the water, even in small quantity. The iron is usually present in the water in the form of bicarbonate or sulphate of the protoxide (ferrous bicarbonate or sulphate), the former being the more frequent form. When the iron is present in appreciable quantity, its presence betrays itself by the water becoming turbid when exposed to the air in an open vessel, and, after a few hours, a reddish brown sediment is found at the bottom of the vessel, the water having more or less regained its clearness. The deposit consists of the iron converted into the condition of insoluble hydrated peroxide (ferric hydrate) by the oxidizing action of the air.

The iron may also be detected by adding a few drops of a solution of red prussiate of potash, which will give a blue coloration in such water. When present in small quantity, the iron may be found by boiling a portion of the water down to about one-tenth its bulk in a dish or flask; the iron, as peroxide, will then be found as a brown sediment, which may be dissolved in a little hydrochloric acid, and the above test applied to the solution.

3. — Examination with a Decoction of Logwood.

A decoction of logwood is an extremely delicate re-agent, showing by the various tints which it assumes the impurities contained in the water. The decoction is made by boiling about 1 oz. of logwood chips in 4 oz. of distilled water for a few minutes, allowing it to stand till quite cold, and then filtering it.

The water to be tested should be poured into the 100 cubic centimetres measure, or into a tall white glass bottle; a few drops of the infusion are then dropped into the water, and the coloration observed without stirring up the water.

The following reactions will be observed: —
Distilled water . . . A brown amber or sherry colour.
Water containing only —
Calcic sulphate or chloride . . . Red amber, becoming red brown.
Magnesic do . . . Amber, becoming more brown.
Calcic bicarbonate. . . . Red claret, passing to a bluer shade.
Magnesic do . . . Red claret, becoming more blue.
Ferrous bicarbonate or sulphate . . . Olive black, becoming blue black.
Alkaline carbonates, carbonate of potash or soda . . . Dark Cherry.
Free acids . . . Light amber.

The depth of coloration is, in each case, in proportion to the amount of the special impurity in solution. When there is a mixture of impurities, the coloration partakes also of a mixed character; but a departure from the standard of distilled water is readily recognized, and should not be considerable.

4. — Organic Matter.

The presence of organic matter in quantity which would prove injurious in the woollen industry, generally betrays itself by the brown coloration which it gives to the water, or by separating as a brown scum when the water is raised to the boil. This brown substance may, however, readily be mistaken for oxide of iron, which it frequently resembles very closely in colour. A portion of it should be removed, dried, and burnt; if it be organic matter it will burn almost completely away; if it be oxide of iron, a red powder will be left.

5. The Dyeing Test.

To test the water, in order to ascertain whether it may be suitable for use for obtaining any particular colours, it is advisable to dye with it in a small way samples of the wool; at the same time, for comparison, samples should also be dyed, using distilled water or water known to be good for dyeing -taking every precaution to use in each case the same weight of mate rials and dyes, and the same temperature and time; and parti cular notice should be taken whether any marked change of colour takes place when the goods are finally rinsed or washed off in the same water.

The particular colours to be tried will readily suggest themselves to the dyer.

These small operations are best performed in an enamelled iron pan, heated over a powerful gas burner.

Having examined the water by the five operations described above, a good knowledge will have been obtained of its capa bilities to fulfil the conditions required of it, and any obnoxious substances will have been detected.

Influence of the impurities contained in water on the operations of scouring, rinsing, and dyeing.

1. — Calcareous and Magnesic Impurities.

Influence on Scouring with Soap.

These impurities, in whatever form they may be present in the water, decompose and destroy as a detergent their equivalent quantities of soap, by converting it into a lime or magnesia soap, which is insoluble and greasy, and not only non-detergent, but it adds to the difficulty of the subsequent thorough cleansing. Every pound of chalk, or carbonate of lime dissolved in water destroys 10 lbs. of soap. The insoluble soap so formed cannot be washed out from the wool or fabric, to which it attaches itself with great tenacity, and is frequently very mischievous in the dye-bath, producing irregularity in the reception of both mordant and dye. I have, therefore, mentioned 7 degrees of hardness as the furthest limit at which it will be found advisable to employ water for scouring purposes when soap has to be used.

Even during the rinsing or washing off the wool or fabric where soap has been used, the mischief is increased by the fresh water acting upon the excess of soap which has to be used to obtain a scour; this excess is also converted into insoluble soap, and is added to that already formed.

Influence on Scouring with Alkaline Carbonates and Urine.

Calcareous and magnesic salts, when heated up with alkaline carbonates, precipitate their carbonates in a powdery condition, which may readily be removed by washing; but as wool generally contains a portion of natural fatty matter which forms a soapy emulsion with the alkaline carbonate, the presence of calcic and magnesic compounds interferes with the detergent action of the alkalies. The bad effects, however, are not so great as when soap has to be employed for scouring.

Influence on Mordanting and Dyeing.

Calcic and magnesic salts, when in the condition of sulphates or chlorides, appear to have no influence over the reception of either mordant or dye; waters containing them act, so far as woollen dyeing is concerned, as pure water.

When the salts are in the condition of carbonates, held in solution by carbonic acid (so-called bi-carbonates), they are often exceedingly troublesome.

1. They diminish the effect of the mordant, and necessitate great care in counteracting this evil tendency by the use of an acid of tartar.

2. They produce a different shade of colour in most cases in the dye-bath, and require great skill and experience to obtain uniform results.

In fact, the dyer has a host of complaints to make against these earthy carbonates, for they blue his cochineal scarlets and the colours of logwood, fustic, and bark, but at the same time the colours loose their brightness, and the strength of colour is not permanent; they destroy his tartar, which expends itself in converting the earthy carbonates into tartrates; they act generally as a diminution of mordant.

2. Impurities in the form of Iron Salts (Ferruginous Waters).

Their influence on Scouring.

With soap they act like the calcic and magnesic salts, producing an iron soap which adheres to the wool, and is more mischievous than even the lime and magnesia soaps, for it seriously affects the colours afterwards dyed upon the wool. With alkaline carbonates (soda ash, urine) the oxide or hydrate of iron is precipitated, which adheres more or less to the wool or fabric, and is a constant source of anxiety and annoyance to the dyer.

Their incluence on Dyeing.

As iron compounds always have the effect of saddening colours, it is hopeless to expect to obtain any bright shades of colour when a ferruginous water is used. Even with the dark and sad shades, and blacks, the use of this description of water frequently produces unsatisfactory colours. I have often seen cloudy and rusty spots on pieces which have been dyed with such water.

3. Impurities in the form of Alkaline Carbonates.

Influence on Scouring.

When the water is not also charged with earthy carbonates, the presence of these carbonates is beneficial rather than otherwise in scouring with either soap or alkaline carbonates.

Influence on Dyeing.

I know of no condition of water which is more troublesome to the dyer than this alkaline condition. In the mordanting it precipitates the bases of iron, tin, and copper salts, and of alum, and reduces bichromate of potash to the condition of yellow chromate, a much less effective mor dant. It acts on mordants in a similar manner to what the earthy carbonates do, but the action is sharper and more decided. Its evil influence can only be prevented by the use of an acid to neutralize the alkalinity of the water.

In dyeing with this alkaline water the greatest care and skill are required, otherwise the colours will be affected; and in the rinsing or washing off, the colours, which may have been set right in the dye-bath, will be thrown altogether wrong again by the alkalinity of the wash-water.

I repeat, I know of no condition of water which is more perplexing to the dyer than this alkalinity; and, unfortunately, it is of too common occurrence in some of the woollen districts of Yorkshire, where the dyer derives his supply from wells, or by boring into the lower beds of the coal measures, which appear to be charged with carbonate of soda.

4. — Organic Impurities.

Waters charged with organic matters in sufficient quantity to give them a colour are not suitable for bleaching wool, as they tend to stain it; but I have not met with any cases in which they have proved prejudicial for scouring or dyeing, except the organic matter be in the form of dye-waters from other works. Even the peaty waters from our Yorkshire moorlands do not seem to have any prejudicial influence on the dyeing of wool or woollen fabric; at any rate, no cases have come under my notice.

5. Impurities in the form of Free Acids or Acid Salts.

I have met with two classes of these waters:–
(a) Waters con taining peaty acids.
(b) Water running from pyritic shales near the surface, which by oxidation charge the water with sulphate of iron. On exposure, much of the iron deposits, leaving the water acid with free sulphuric acid. Both these waters are exceedingly injurious to steam boilers. The acids become concentrated by evaporation in the steam boiler and attack the iron plates.

A new boiler, for which the first class of water was used, had its half-inch plates perforated after three months' use, and the tubes of a multitubular boiler had to be removed after using the purples; they blue the reds of his red woods; they strengthen second description of water for a few months. Both waters were entirely corrected by the addition of a little lime. They neither of them contained a trace of lime.

These waters are unsuitable for the treatment of wool. The second one decomposes soap and liberates the fatty acids con tained in it, which attach themselves to the wool in the same manner as the lime and magnesia soaps which I have already described.

(To be continued.)

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