CHAPTER XVI

RESIST AND DISCHARGE STENCILLING

Travelers in Japan inform us that, with their customary ingenuity, the natives there have developed the use of stencils to a point which quite matches the best achievements of our modern calico printers, even though backed by good dyeing chemists. When a young lady there wishes a new dress, she will draw, perhaps with the help of her best young man, and certainly with the advice and criticism of her family, her favorite design on a piece of brown paper, cut it out in stencil form, and send it to the local dyer, with the proper amount of calico or silk or what not, to be properly applied.

Now, in most cases the dyer is instructed to put the pattern on the cloth in colors, blue, black, red, yellow, or mixed shades, and this he does, much as my readers were taught to do in the last chapter, by painting on a stencil paste, to be fixed later by steaming.

The Japanese dyer, by the way, has a great advantage over the American craftsman in his steaming apparatus. No matter how small his place, or how poor his equipment, he always is provided with a neat and satisfactory steam chest, consisting of a copper pot set in a brick or stone fireplace, to hold the boiling water, and above it, a close-fitting box with sides made of lacquered paper, double jacketed to avoid condensation in cold weather, which can be kept full of dry steam for hours at a time, and in which the stencilled goods can be steamed thoroughly and well without fear of spoiling them.

Sometimes, however, the color is to be applied in another way; the cloth itself is to be colored blue or red or black, and the pattern is to be light, either pure white or some light color on a dark background.

The Japanese dyer, from time immemorial, has known how to do this properly, by means of a “Resist.” He prepares a resist paste which he carefully applies to the cloth through the stencil. This is allowed to dry, the cloth is then dyed, and, after the color is properly fixed, it is all thoroughly scrubbed, and the paste, washing off, leaves the cloth, underneath, in its original color.

_Resist Stencil Paste._—This process of resist, ancient as it is, is used in Japan to this day, and many, indeed most, of the stencilled towels and piece goods that come from there are done in this way. It has the advantages, especially for the craftsman, over the Direct Color process, in that the color, being applied in a dye-bath, can be fixed readily and uniformly, without the bother and uncertainty of a steaming process. Through a friend, a well-known dyeing chemist, who has travelled in Japan, I learned the composition of the Japanese Resist Paste. They mix rice flour, wheat bran, and a little quicklime (the calcium oxide of the chemist) with water and boil it to make a paste. This they strain, and then they stir in some powdered carbonate of lime (powdered chalk), which thickens and gives some body to the mixture. The paste thus formed is applied, as a rule, not with a brush but with a flat wooden instrument or spatula, with which the paste is laid on as with a trowel, and further, to get the dead white effects so commonly noticed, the paste is put on the back of the cloth as well as on the front.

My friend also explained to me how the Japanese were able to get irregular shaded effects with their stencil work, and at the same time to furnish such beautiful and intricate hand-made work, at such absurdly low prices. These goods are made of very thin porous materials, and the dyer applies with his trowel the thick resist paste, through the stencil, to one piece after another, laying each one, as fast as it is stencilled, carefully on top of the previous one, until a pile has been formed of ten or more separate pieces. This pile is pressed very tightly together, and then the dyestuff, as, for instance, Indigo in solution and thoroughly reduced, is poured on to this mass of goods, soaking through from one to the other, but always kept out of the white parts by the double coating of thick paste.

After a few minutes these pieces are carefully taken off, one by one, exposed to the air until oxidized, and then thoroughly washed until the paste and loose color have all disappeared. For an example of Japanese resist stencil work, dyed in an iron spring, see Plate III.

[Illustration: PLATE V. JAPANESE TOWELLING DYED BY IMMERSION IN IRON SPRING. THE WHITE PATTERN IS CAUSED BY RESIST STENCILLING]

_Resist Stencilling with Sulphur Dyes._—Without lavishly copying the Japanese practice it is possible to get very interesting results by using suitable dyestuffs with a simpler paste.

The most useful dyes for this purpose are the Sulphur dyes, which, as the student will remember, can be applied in the cold, with very short exposure to the dye-liquor, and are fixed firmly by exposure to the air, giving results fast to light and extremely fast to washing. A paste made from wheat flour, thickened a little with an inert powder, like powdered chalk or zinc oxide, will work fairly well, acting as a purely mechanical protection to the fibre. But much better results can be obtained by adding to the paste as much as it will absorb of the easily soluble chemical, zinc sulphate, which acts chemically in resisting the action of these particular dyestuffs.

The Sulphur colors, as before explained, are kept in solution in the dye-bath, by the presence of sodium sulphide, and when this is absent or is destroyed by any cause, the dyestuff is precipitated as an insoluble, inert powder. Now, when zinc sulphate comes in contact with sodium sulphide it at once decomposes the latter, forming a white precipitate, zinc sulphide, which has no action at all on either dyestuff or cloth. Accordingly a paste containing zinc sulphate has far greater efficiency as a resist than any mixture that acts purely mechanically.

Resist stencil pastes can be obtained, in tubes, at moderate prices, but can also be readily prepared by making not too stiff a paste, with wheat flour thoroughly boiled with a saturated solution of zinc sulphate instead of with water, and then stirring into this paste some powdered chalk or zinc oxide, until of the proper consistency for stencilling.

To use this paste, the cloth, as usual, should be washed free from dressing, and after being smoothed with a hot iron, should be slightly dampened. The paste is then brushed through the stencil on to, and into, the cloth, which is then allowed to dry. The dye-bath should then be prepared of Sulphur dyes carefully dissolved, in a separate cup or saucepan, in a hot solution of sodium sulphide and sodium carbonate (soda), and added to cold water in the dye-bath.

A few drops of “Turkey red oil” added to the dye-bath helps to prevent a thick scum from forming on top of the liquor, while the addition of a tablespoonful of salt dissolved in a little hot water helps the rapidity and depth of the dyeing.

Plenty of color should be used excepting for very light shades, for the dyeing should be done just as quickly as possible. For silk some syrup should be added.

The stencilled cloth is then quickly moistened in cold water, placed in the dye-bath, kept there two or three minutes, below the level of the liquid; it is then taken out, the liquor drained off, and after a minute or two, wrung off; the cloth is then shaken out, and exposed to the air, for some ten minutes, to set the color. After this it is well washed in a boiling soap bath, and, as the paste washes out, the stencilled pattern will show light against the dark background.

The whiteness of the pattern depends, of course, upon the skill with which the paste has been applied, and the care taken to prevent it from washing off before or during the dyeing process. It is difficult, though not absolutely impossible, to get as sharp and clear-cut results as those of the Japanese, for instance. But, on the other hand, with a dark background it is often, indeed generally, more pleasing to have the white patterns softened and not standing out too vividly.

In our laboratory we have had considerable success with this process. And some of our friends and students have used it with very good results upon articles of clothing, which, made of linen, calico, etc., must be fast to severe washing as well as to light.

Of course, it is perfectly easy to alter the color of the background, as in other classes of resist work, such as Tied and Dyed work, for instance, or Batik, by either starting off with colored cloth which is protected all through by the resist paste, or else by covering the stencilled and dyed goods, afterwards, with some shade which will soften and harmonize both pattern and background. For this covering shade, which need not be very fast to washing, but must be distributed uniformly over the whole cloth, the student will find the Salt colors very useful.

_Discharge Stencilling._—Though it is not certain whether this process is known to, and used by, the Japanese, it is not a difficult matter, with modern dyes and modern chemicals, to get interesting results with it. There are two distinct and separate ways open to the dyer for discharging, i.e., destroying his dyestuffs, whether they are dyed on cloth, or whether, as is not infrequently the case with amateurs, they are present as a stain on his hands and fingers. In each case, however, care must be taken, as may easily be imagined, to use such chemicals as will spare the materials, whether cotton and linen, or nails and skin, while attacking the coloring matter.

(a) _Discharge by Oxidation. Chlorine Compounds, Bleaching Powder, etc._—In the first place, chemists have long known that certain chemicals, more particularly the powerful gaseous element known as chlorine and certain of its compounds, have the power of permanently destroying coloring matters by oxidizing or burning them.

At first this was done by using chlorine itself, or a water solution of chlorine. Later, however, it was found that on passing chlorine into some caustic alkali, like quicklime, or caustic soda, or caustic potash, these would absorb immense quantities of chlorine which would be again given out, as desired, on the addition of acid, or even, though very slowly and gradually, by the action of the carbonic acid gas in the air.

The lime compound, which contains more chlorine than the others, and has the great advantage of being dry, has long been known as chloride of lime or as bleaching powder, and has been, and is, commonly used from one end of the world to the other as a quick, ready, cheap source of chlorine either for bleaching or for disinfection. The potash and soda compounds, known respectively as Labarraque’s solution and Javelle water, are less active and powerful than bleaching powder, but have the same general properties.

Over a hundred years ago, very soon after the discovery of the bleaching properties of these compounds, chemists began to use them, not only for decolorizing and whitening raw cotton and linen cloth, but also for discharging the color in patterns from dyed goods. The process was not a difficult one, and is used to this day to some extent in the calico printing mills. The cloth is first dyed to shade, fixed, and dried. The pattern is then printed on with a paste containing some solid organic acid, like citric acid or tartaric acid, dissolved in it. After drying, the printed cloth is passed through a bath of bleaching powder in water, possibly with a little weak alkali added, to be sure that no free chlorine is present; and wherever the bleaching powder meets the acid the cloth is decolorized, but the rest of the cloth comes out of the bath without being much, if at all, altered in color. Of course, on coming out of this bath the cloth must be thoroughly washed to get rid of any traces of chloride of lime, which otherwise, on exposure to the air, would play havoc with the rest of the colors.

This process worked very well with the old vegetable dyes, and, every now and then, some craftsman, of an experimental turn of mind, revives it for stencil work. The dyed cloth is stencilled with a paste made of wheat flour boiled with a saturated solution of citric acid, it is dried, and then passed through a bath of bleaching powder in water, say two or three tablespoonfuls to the gallon. It is generally best to stir in a few drops of a soda solution to the bath, till all smell of chlorine has gone, or else the background may be affected. The stencilled cloth is dipped in this bath, and kept there for a few minutes, until the bleaching process is well under way, and then taken out, and washed in hot soap and water, and rinsed well.

_Advantages and Disadvantages of Bleaching Powder Discharge._—The chief advantage of this process is that it is very cheap and the materials can be bought at almost any grocery. The disadvantages are, however, important. As long as it is confined to easily discharged, comparatively fugitive, colors, it will destroy the color all right in the stencilled parts, although the bleaching powder bath is apt to attack the color in the body of the cloth, and the outlines of the pattern are apt to be soft and irregular because of the escaping chlorine, where the citric acid is acting.

When, however, very fast dyes are being used, as for instance, the Vat colors or, indeed, a great many of the best dyes in all the classes, the action of chlorine is very slow, and slight, and, in order to really destroy the color both the acid and the bleaching powder will often have to be so strong that the chlorine set free will destroy the fibre as well. For the term “fastness to light” implies, as a rule, fastness also to oxidation in general, and dyes like the best modern ones which will let the cloth rot away from under them, when long exposed to the weather without changing color, are very apt also to keep their color, even when the cloth is _burnt_ away from under them by the action of chlorine.

Accordingly, this process is distinctly one that needs careful experimentation before it is tried on any important piece of work. There are plenty of dyestuffs among the Salt colors, and also among the Sulphur colors, which discharge well with chlorine. And the calico printer, working, as he generally does to this day, with comparatively fugitive dyes, and weighing accurately both acid and bleaching powder, can generally get good results with it. But there is always the disadvantage, that the least excess of chlorine will attack and tender the cloth, and the better the dyestuff, as a rule, the stronger the oxidizing agent must be to discharge it.

(b) _Discharge by Reduction, Hydrosulphite, etc._—The wary craftsman will find the process much less dangerous to the cloth, and not much more difficult, if instead of trying to _oxidize_ the dyestuff, he attempts to discharge it by _reducing_ it; or, in other words, if instead of trying to burn it out, he tries to take the oxygen away from it.

It so happens that in a vast majority of cases a dyestuff becomes decolorized by reducing it, just as well as by oxidizing it. There is, however, a difference. When the color is oxidized, it is burnt up and destroyed forever. When it is reduced, however, it is, in many cases, only decolorized and not destroyed; and on standing in the air it is apt to take up oxygen again, and to regain some, at least, of the original color. On the other hand, while any oxidation process is liable to attack the cloth as well as the color, the reducing agents now in use have no effect upon the materials, even when powerful enough to act on the very fastest dyestuffs.

As before mentioned, the most satisfactory reducing agent at present known to dyers is hydrosulphite of soda, and this can be incorporated in a paste, and used for discharge stencilling. It is, however, as a rule, more satisfactory to use the more expensive, but more permanent hydrosulphite compound, described, in the last chapter, as acting only when heated.

The reducing stencil paste can be easily made by mixing with some “gum dragon” or flour paste, as much as it will hold of a saturated solution of the “Stencil Salt.”

The student should experiment with the different dyes and classes of dyes before attempting a serious piece of work; but in general, all the Salt colors and the Acid colors will discharge readily with this paste, and remain colorless. The Vat colors and the Sulphur colors can also be reduced to colorless compounds, but it is not always easy to wash them out of the cloth after the reduction, and, if they remain in it, they are apt to regain their color, on standing in the air.

The dyed cloth, carefully washed and pressed and dampened, is stencilled with the above paste and allowed to dry. When dry it is steamed, as described in the last chapter, and it will be noticed that when a certain temperature is reached the color will be discharged. As soon as possible afterwards the cloth is to be washed in a hot soap bath to remove the reduced color compound (which, as a rule, has little affinity for the cloth) and to get rid of the paste. Then the cloth is dried and finished.

When trying this process with the Vat dyes it is best to soak the cloth directly after steaming, and before soaping, in a warm bath containing a little free caustic soda (remember this is apt to burn the fingers) because the reduced colors of this class are not, as a rule, soluble in water, and are apt to oxidize again in a soap bath.

_Results._—In following up these various experiments in our laboratory we have not used this process in much as the Resist stencilling, but there is no reason why it should not give just as good results. Indeed, the craftsman will probably find, after a little practice, that it is easier to get clear white patterns with this than with the other. It has the disadvantage of requiring the rather bothersome steaming process, which reduces its value for many purposes. Still it will often be found that simply ironing the dried stencilled cloth with a hot flatiron, with a damp cloth between, will cause the reduction to take place quite satisfactorily.

The chief advantage of this process over the other is that, as the dyeing is done before and not after the stencilling, it is possible to get the exact shade of background required. While, in the resist stencilling every minute, almost indeed every second that the stencilled goods are left in the dye-bath, is liable to obscure the pattern. And it is hard to get first-class results, as regards fastness to rubbing and washing, and it is impossible to match shades, when working so hurriedly.

Then, too, this discharge process permits the use of almost every color on the list, while the resist process practically confines the craftsman to the use of the Sulphur dyes only.

Those who are interested in this line of work are advised to try these two processes upon silk, where very beautiful and interesting effects can be produced with but little difficulty. The resist process, using Sulphur colors, gives quiet soft tones on silk, fast to the hardest kind of washing. But brighter shades, equally fast to light, and fairly fast to washing, can be made with the discharge process by using Salt colors.

For ordinary work the Acid dyes, of course, would be used, and these, too, as a rule, discharge readily.