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The art of staining and dyeing leather, part III

Published September 1902

Dyeing Morocco and similar leather

Dyeing Morocco and similar leather
image  Dyeing Morocco and similar leather

The operation of dyeing with aniline dyes is, in one respect, less easy of an accomplishment than with the dye-wood liquors. With the latter dyeing materials even tones can be obtained at very little trouble. With aniline dyes there are several influences at work which hinder the production of an even tone of colour on the leather. For example, the higher the temperature at which the dye liquor is used the greater will be the intensity of colour produced, also the strength of the dye liquor determines in a remarkable degree the actual tone of colour produced on the leather. A weak dye liquor will give a colour that is no indication whatever of the colour that can be produced with the same dye, when the dye liquor is a strong one. Also if more than one piece of leather is to be dyed, the piece first dipped in the dye liquor will be much more intense in coloration than the next and subsequent pieces. Aniline dyes have such a great affinity for any material of an organic nature that they combine therewith with great rapidity, more so according to the strength of the dye liquor. Yet again, the length of time in which the leather is submitted to the action of the aniline dye bath greatly influences the colour produced.

If the immersion be carried on too long, or the dye liquor be too strong, the colour exhibited on the leather will present a bronzed appearance. Yet with all these apparent difficulties, the colours which can be produced by means of aniline dyes are so much more brilliant than what can be obtained with dye-wood materials, that the novice will do well to practise with the former.

One of the best methods to pursue, because it minimises the troubles above referred to, is to have several baths of dye-liquor, each of different strength, and to submit the leather first to the action of the weakest one, and then to the next stronger one, and finally, to the strongest one of all. By this method the leather is but faintly coloured at first, and any unevenness of coloration is corrected as it successively passes through the stronger dye baths, until, finally, it has assumed the exact colour desired. This method is very much to be preferred to prolonging the time of immersion of the leather in the dye liquor, and as a matter of fact, the desired results are obtained with comparatively few failures.

Preliminary operations in Dyeing with Aniline Colours

Have three or four earthenware vessels to hold the hot dye liquor, and a copper one to warm it in. Instead of a dyeing bath, a zinc or copper tray having a rim about two inches high should be used, when the dyeing may be effected by dipping, in which case a deep earthenware pan (such as is used in the kitchen for storing bread in) should be used. Prepare the dye liquor according to the quantities of ingredients named in the formulae, and, when the dye liquor has been made and filtered, divide it into three (or four) equal quantities to one quantity add three times its bulk of clean water, and to the second quantity add its own bulk of pure water, and call the first quantity No. 1 dye liquor, the second quantity No. 2 dye liquor, and the undiluted portion No. 3 dye liquor. Thus No. 1 would be composed of one-third dye liquor and two-thirds water. No. 2 would be composed of half dye liquor and half water, while No. 3 would be dye liquor of full strength, being undiluted.

Now, when carrying out the dyeing process, put the leather into No. 1 dye liquor first and for the prescribed length of time, then into No 2 dye liquor, and finally into No. 3 dye liquor, observing to keep the temperature of the dye liquor to the proper degree, and also to regulate the length of time of the immersion of the leather. Any unevenness of colour in the lirst two dye liquors will be corrected in the final one by a prolonged immersion before removal from this dye liquor.

Wash the dyed leather in clear water and hang it up to dry, when dry finish it with a finishing gloss. If more than one pair of pieces of leather are to be dyed then make a fresh bath of dye liquor for the final bath (undiluted), and after dyeing the first pair of skins repeat with the dye liquor, and put the second pair of skins first into No. 2 dye liquor, then into No. 3, and finally into the fresh dye bath. By this means an economy of dye liquor is effected, but what is of greater importance a better evenness of coloration is produced. To ensure evenness of coloration the addition of phosphate or sulphate of soda to the dye liquor is frequently made (vide infra, while in some cases the skin should be moistened with a weak solution of either sulphuric acid or soap and water, according to the nature of the aniline dyes made use of, viz., whether it requires an acid or alkaline base to work on.

In dyeing leather it is usual to place flesh side to flesh side, whereby the flesh side does not become fully dyed, and a saving of dye liquor is obtained; but, of course, for the amateur worker, who will probably not care to operate on a whole pair of skins at one operation, this is not necessary, as the amount of dye liquor he will require is very limited. While the leather is in the dye liquor it should often be moved about and examined from time to time to judge to the tone of colour obtained at each stage. When sufficiently coloured, wash the dyed skin in plenty of clean water and hang up to dry.

The subsequent finishing operations consist in giving a slight smear of oil (fish, sweet, or sperm) on the dyed side, and then laying on a thin coating of gum dragon mucilage—prepared as given below—or else a solution of egg albumen mixed with glycerine.

Gum Dragon finish is prepared by soaking 1 oz. to 2 oz. of gum tragacanth (i.e., commonly called gum dragon) in one gallon of cold water for several weeks, and then straining the thick jellylike mucilage that is produced, and picking out all white lumps,, and to the strained mucilage adding one to two fluid ounces of castor oil per gallon of mucilage. This finish is laid on the dyed skin by means of a roll of felt, which is dipped in the mucilage and then lightly rubbed over the dyed leather, and, when dry, the coloured leather is ready for use as required.

Egg Albumen preservative finish is prepared by mixing 30 fluid ounces of egg yolk with 1 fluid ounce of glycerine, and then compounding them with water in the proportion of 1 oz. to 2 oz. per pint of water.

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Formulæ for Dyeing Leather with Aniline Dyes

The following list of formulæ will be sufficient for the novice to try a "’prentice hand" in, and should not be found at all difficult. Any of the preservative finishing glosses can be used with the aniline-dyed leather so as to impart a finished appearance and prevent the colour fading.

H. C. S.

 

 Lilac Colour

 Red Colour

 Red Colour

 Crimson Colour

 Canary Yellow Colour

 Full Yellow Colour

 Full Yellow Colour

 Light Green Colour

 Dark Green Colour

 Light Blue Colour

 Brown Colour

 Nut Brown Colour

About this article

Acknowledgement for the banner image goes to Vince Gx on Unsplash. The photo is not from the article and is added as an artist's impression. The colours shown on this page are an artists impression of the colour discussed and are provided as suggestions only.

This article is a reprint of an existing article, published in The House, September 1902. It is the intent of this website to present this article in human and machine readable form. Format and editing changes have been made. This article is provided for the purpose of enjoyment only.