DYEING DIRECTIONS
These dyes are all applied, just like indigo, in an alkaline hydrosulphite vat. The colors are applied in paste form, usually 20% strong, or at any rate equivalent in strength to a 20% paste of pure indigo. Care must be taken to thoroughly mix and stir up this paste with a glass rod, in the original package, each time it is used, so as to keep its composition uniform.
The proper amount, to be determined only by experience, is first thinned with a little hot water, and then stirred into the dye-pot, two-thirds full of hot water, about 140° F. (This is well below a boil, and yet hot enough to slightly scald the tips of the fingers.) To this is added caustic soda, in the proportion of two to three spoonfuls to each one of the color, the amount of soda being proportionately greater for light shades than where large amounts of color are used.
After this has been dissolved the dyestuff is reduced by adding slowly, with constant stirring, spoonful after spoonful of the powdered sodium hydrosulphite until the bath clears and generally the color changes. In most cases, as with indigo, the completion of the reducing change can be told by a marked alteration in the shade of the bath.
Thus, in general, the blue dyes, like indigo, turn yellow or orange when the proper amount of hydrosulphite is added. For the other colors there is no general rule. Thus Indanthrene Yellow (Badische), when reduced, is blue—while the Helindone Yellow (Metz) is blood red. Helindone Scarlets (Metz), when reduced, appear green, while the Thio Indigo Red and Scarlet have about the same color, when reduced, that they have when oxidized.
The best way to tell whether the bath is in proper condition is to dip a piece of white blotting paper into it, and notice, on taking it out, whether the color is in specks or is dissolved. On standing in the air for a few minutes the color should become oxidized, and firmly fixed to the paper. As a rule these Vat colors should be reduced warm, because, in many cases at least, the reduced color does not dissolve in a bath of cold alkali. In most cases, however, after having been reduced at a temperature of about 140° F, the bath may be allowed to cool considerably, before it loses its dyeing value. This enables these colors to be used for Batik, or other processes where the temperature must be kept below 80° or 90° F. The dyestuffs which can be thus used will be found marked with an asterisk in the list of selected dyestuffs above.
The well-wetted materials are placed in the reduced dye-bath, and stirred and worked for five or ten minutes, or longer, according to the depth of shade experienced. For full shades, however, as in the case of indigo, it is much better to build up the color by successive dippings than to try to put it all on in one bath. For heavy goods the addition of a little Turkey red oil, about half a tablespoonful to the gallon, is an advantage, though not absolutely necessary. When thoroughly impregnated with the dye-liquor, the goods are taken out, wrung carefully, two or three times, to remove the waste liquor as evenly as possible, and then shaken out and exposed to the air for fifteen or twenty minutes. They are then boiled in a soap bath for about twenty minutes, and then well rinsed, and dried. This hot soap bath, as before mentioned, is of great importance in most of these colors, not only for getting rid of loosely fixed dyestuff, but for oxidizing and fixing the color itself.
For dark shades it is well, as in the case of the Sulphur colors, to add salt—three or four tablespoonfuls per gallon of dye-liquor—to the bath, taking care to have it well dissolved before the goods are entered. This is always done when dyeing with Helindone Yellow 3GN, Metz.
The shades of these new Vat colors are extremely bright and clear, and, by combining these properly, any desired effects may be produced. The splendid series of reds and scarlets for the first time allow the characteristic shades of Turkey red to be obtained, in one bath, and of at least equal, if not of superior fastness to the original. One peculiarity of these colors is their extreme fastness, not only to light and washing, acids and alkalies, but also to various oxidizing agents, such as chloride of lime or bleaching powder. Accordingly goods properly dyed and finished with these dyestuffs can be entrusted with safety, so far as the color goes, to agencies which would speedily ruin fabrics dyed in any other manner.
Chapter VII
THE BASIC COLORS
In an earlier chapter it was mentioned that the modern dyestuffs originated with the discovery by Perkin, in 1856, of the violet coloring matter known as Mauveine. This dye was made by the oxidation of the then rare chemical, aniline. Following this discovery, other chemists, especially in France and Germany, soon obtained from the same chemical or from substances very closely resembling it, a considerable quantity of powerful and brilliant dyestuffs of the same general character.
The original Mauveine was before long superseded, first by Hofmann’s Violet, and then by a very important series of violet and purple dyes known as Methyl Violet, with shades ranging from 6 or 7B for the deep, full purples, to the 6 or 7R for the very red shades. These violet colors have never been surpassed, or even equalled by any other dyes for brilliancy and richness, although, in common with almost all the other dyes of this class, they are not fast to sunlight.
Another extremely powerful and brilliant color of this class, used considerably to this day although discovered nearly fifty years ago, is the dye often called, from its origin, Aniline Red. It was, however, named by the German manufacturers, Fuchsine, from its rich, full, crimson shades, resembling the deep tints of the flower, fuchsia, while the French, who discovered and manufactured it soon after the close of Louis Napoleon’s Italian campaign, called it Magenta, after the famous victory of that name.
About this time some German chemists discovered and introduced a full, rich, brown dye, still largely used for dyeing leather (kid gloves and the like), and, naturally enough, gave it the name of Bismarck Brown. And at approximately the same date was discovered the very valuable blue dyestuff, perhaps the best of the whole class, with quite a range of full, deep shades, and with considerable fastness to light, called Methylene Blue.
General Properties.—The early colors of this group are the dyestuffs properly known as the “Aniline Colors” because of their origin; although this name has been applied, loosely, to all of the thousands of artificial dyestuffs without regard to their source of composition. To the chemist, their chemical structure and their behavior toward reagents, such as acids and alkalies, naturally suggested the name “Basic Colors.” This means that they are substances with strong affinity for all sorts of acids, with which they form more or less stable salts, while they can be liberated from these salts by the action of stronger bases, such as ammonia, or the fixed alkalies, soda and potash.
Application.—These facts were discovered by Perkin while trying to introduce his Mauveine into the dyeing industry, and he discovered the methods, used to this day, for applying these dyes to the different textile materials. He found that the dyes of this class have a strong affinity for the different animal fibres, such as wool, silk, leather, etc., all of which seem to possess some acid properties of their own; but pure vegetable materials, like cotton, linen, and paper, from which all impurities such as vegetable acids, gums, etc., have been removed, have no affinity at all for even the most powerful of the Basic dyes. A cotton handkerchief, boiled for hours in a strong solution of Methyl Violet, can be washed in a few minutes clear of every particle of color, while a piece of silk or wool, soaked for an instant in the same dye-bath, will be permanently stained, deep and full.
Cotton, Linen, etc.—In order to fasten these dyes to vegetable fibre it is necessary to give the latter a distinctly acid character, and this was done by Perkin in a manner still used. He steeped the material for several hours in a hot bath of the acid vegetable compound, tannic acid or tannin, found so largely in hemlock and chestnut bark, sumac leaves, nut-galls, and the like; and then loosely fixed the tannin, thus absorbed, by a weak bath of tartar emetic. Cotton or linen fabrics, thus “mordanted,” will combine with the Basic dyes as readily and as firmly as any animal fibre, and the resulting colors, while not, as a rule, fast to light, are extremely fast to washing.
Since the introduction of the direct cotton dyes, both Salt colors and Sulphur colors, this method of dyeing, for skeins or piece goods, has been largely discontinued; but, by using a modification of this process, enormous quantities of Basic colors are still employed, on cotton and linen, in the manufacture of calicoes, organdies, and other printed fabrics.
Curiously enough the Salt and the Sulphur colors, in almost every instance, possess sufficient acid properties of their own to act as very fair mordants for the Basic colors. Accordingly, it is not uncommon for dyers to “top,” with Basic colors, cotton or linen goods dyed directly. In the case of the Salt colors, this increases their fastness to washing, and with Sulphur colors it makes the shades more brilliant.
Most vegetable materials that are used in a more or less natural condition, like straw, raffia, grass, wood-shavings, jute, and the like, contain enough of this natural tannic acid to act as a mordant for the Basic colors, which may in this direction be used as direct dyes.
Wool, Silk, etc.—For animal fibres, such as wool, silk, furs, feathers, etc., the Basic colors have been almost entirely superseded, in commerce, by the class of dyestuffs known as the Acid colors. These occur in much greater abundance and variety, and can be applied with less danger of spoiling the goods by uneven results. For leather, on the other hand, the Basic colors are still largely used, especially for dark shades, or when fastness to light is not particularly desired. On bark-tanned leather, which is full of tannic acid, they take hold particularly well, and are often more convenient to work with than the Acid colors, although they do not, as a rule, give such even results.
Uses.—On a small scale it is hardly worth while for the amateur to try to use these Basic colors for dyeing either cotton or linen. The difficulty of correctly and evenly mordanting the goods is quite as great as that of applying the dyes afterward. And the Sulphur colors and Vat colors will be found quite as fast to washing as the best mordanted Basic colors, with the additional advantage of being very much faster to light, as well as easier of application.
By using some of the methods of the calico printer, it is possible to employ these dyes, with some success, for stencilling. But even for this purpose, excepting, perhaps, on silk, the modern Vat colors are more convenient, as well as being infinitely more permanent to light.
Disadvantages.—The chief drawback to the use of these dyes is that they are not fast to light. Several of them—Methylene Blue, for instance, and Methylene Heliotrope O (Metz)—are fairly fast, but the rest, especially in light shades, and on transparent or translucent fabrics, are liable, when exposed to sunlight for any length of time, to alter their shade to a very marked degree.
For dark shades this is not so noticeable, for, when goods are strongly colored, the effect of the sunlight on at least the deeper portions of the fibre is largely counteracted by the color of the goods themselves. So, too, an opaque material, like leather, will hold the same shade of color distinctly longer than silk or, especially, artificial silk, where the sunlight strikes through and through the fibre, without any protection at all. But, generally speaking, these dyes will not stand strong sunlight.
Nor are the shades of these Basic dyes, as a rule, as attractive as those of other classes. The strong and brilliant, not to say coarse, shades of Methyl Violet, Malachite Green, Aniline Red, and the rest, which created such a sensation when they first appeared in the early sixties, were the particular colors which provoked John Ruskin to vehement, if not unparliamentary remarks. When unmixed they certainly do harrow the feelings of those artistically inclined, as much now as then. They are rarely seen now, for the taste of the public has been sufficiently educated to make a demand for softer shades. As before explained, nothing is easier than to soften these fierce, harsh colors to most beautiful and harmonious tints by mixing into them a mere trace of their complementaries.
Advantages.—In spite of all that can be said against them, these cheap, brilliant, and very powerful dyes are not to be despised, and should still be found in the outfit of a well-equipped dyer. For straw, raffia, chips, willow, and other materials used so largely for hats and for basket-work, these dyes are distinctly valuable, and, if supplemented by fast Acid colors for light shades, or for particularly fast effects, will be found satisfactory enough. So, too, for leather they will be found extremely useful, excepting where delicate shades, fast to light, are required.
Some kinds of artificial silk, also, especially those made from nitro-cellulose and hence possessed of acid properties, dye far better with these than with any other dyes, although, as explained above, the colors will be far from permanent.
For the craftsman, the fastness to washing of these dyes is a matter of very little importance, because they are used by him so exclusively upon materials such as basketry, leather, and artificial silk, which are never exposed to rough handling in boiling soap and water.
As regards their fastness to light, the greater number of these must be classed as belonging to the fourth class, i.e., distinctly fugitive in character. On the other hand, some special ones can be selected from the group which are not only distinctly faster than the rest, but are fast enough to be well up in the third class, or can at a stretch, be placed in the second class, i.e., can be considered as satisfactory, at any rate, against any but very severe exposure.
The Fastest Basic Colors.—Among these may be placed the well-known dyestuff, Methylene Blue, perhaps the most satisfactory of the whole class. A very good color also is Methylene Heliotrope O (Metz), which, while less brilliant, is far faster than the many brands of Methyl Violet, Hofmann’s Violet, and the rest, which to most dyers are the characteristic basic violets.
For blacks, many composite dyes are on the market, made by the different color houses, known as Leather Blacks. These are fast enough, for deep shades, but not to be trusted when thinned down to form greys. The fastest individual basic black is Diazine Black, (Kalle), and this should be used for the lighter shades.
The Red and Yellow colors are distinctly less satisfactory. None of them can really be considered better much than third class. Of the Reds the best is probably the color known as Safranine, different brands of which, giving as a rule the yellow shades, are manufactured by the various color houses; one brand being about as fast as another. For the bluish shades of red, probably the fastest is Diazine Red, (Kalle).
As regards Yellow, the list is even more unsatisfactory.
There is a very beautiful golden yellow, known as Auramine O, manufactured by most of the color houses, which, however, is hardly fast enough to be in the third class. This dyestuff, by the way, is injured by boiling, and therefore should never be used in a dye-bath heated to over 130° or 140° Fahrenheit. Less pleasing in shade, but somewhat faster to sunlight, are the rather orange or brownish yellows known as New Phosphine G (Cassella), and Methylene Yellow (Metz). Somewhat brighter colors, though less fast to light, are produced by Thio flavine T. None of these, however, compares in fastness to the selected colors of any other class in this book.
The various brands of the common dyestuff, Bismarck Brown, are largely used for leather, and while probably inferior in fastness to any of the colors mentioned above, are not found in commercial practice too fugitive to be pretty satisfactory. When, however, materials are liable to be exposed for any length of time, two or three weeks in succession, to direct powerful sunlight, it will generally be advisable to use mixed browns made from fast Acid colors.
Upon the whole, although we are still frequently called upon to employ them, they must, from the craftsman’s standpoint, always be considered as untrustworthy. They should, therefore, never be used where dyestuffs of any other class can be made to take their place.