PATTERN DYEING
The preceding general principles have been outlined with all-over dyeing especially in mind. We now come to the consideration of pattern dyeing, where in order to produce a design it is necessary to dye chosen parts of the fabric and keep the dye away from other parts. All that has been said with reference to making all-over dyeing efficient applies equally well to pattern dyeing. If possible, everything that is done to make all-over dyeing successful should be done in pattern dyeing to obtain a corresponding success.
Practically, however, we find it impossible to carry out some of the steps. For example, in the usual block printing, we do not have the problem of handling the fabric in a dye-bath, but rather that of handling dye on the fabric. Here we must take special steps to get the dye well into the fiber and secure the results obtained from the large dye-bath in all-over dyeing.
The fabric must be prepared for pattern dyeing in the same manner as for all-over dyeing. It is just as essential that it be clean, free of sizing, with its fibers soft and absorbent. Attention has been called to the pains taken by the Orientals in the preparation of their fabrics for decoration. We must not jeopardize our success by omitting to boil out new raw material and to clean old material.
This washing before dyeing also brings about any shrinkage that is to occur, and of course this must be done before the design is traced on the cloth, otherwise one could not intelligently work to dimensions.
A dyed pattern may be produced in several ways:
1. The dye is applied to the desired parts of the fabric and means taken to set it there without it spreading to other parts. This is known as direct coloring. Block printing and stenciling, as ordinarily done, are examples. Calico printing is an industrial application of the method.
2. A resist of some kind is applied to parts of the fabric to prevent their taking the dye, after which the fabric is treated in a dye-bath. Batik decoration and tie-dyed work both fall in this class. Stencils and print blocks may also be used in the application of the resist.
3. A “discharge” is put on parts of previously dyed goods, which either removes the color where it touches, or else alters the shade. Different discharges are used according to the nature of the dye and the goods. Some chemicals used as discharges are liable, unless skillfully handled, to attack and tender the cloth. The method belongs rather to the industrial world where abundant apparatus and trained dyeing chemists are available. It is not, however, beyond the skill of a good craftsman who has acquired some experience with dyes.
The dye for direct coloring is applied in liquid form, sometimes thickened into a paste by use of gums, starch, etc. Often mordants or other assisting chemicals are incorporated into the mixture. In block printing this color mixture is brushed on the block, which is then imprinted on the fabric in the desired place, and the color driven into the fiber with pressure or a sharp blow. Stenciling is done by brushing the color mixture through the open parts of the stencil, or by blown stenciling in which a volatile color mixture is sprayed with an atomizer.