Page:The New International Encyclopædia 1st ed. v. 19.djvu/218

* TEXTILE PRINTING. 174 TEXTILE PRINTING. smooth flag of sandstone, covered with securely fastened blankctinj;. Over this table the fabric was spread. The thickened color was spread on a woolen clotli, upon which the printer applied the block and then stamped it upon the cloth. It required great skill and experience on the part of the printer to dip up the color evenly and in the right amount upon the block and then to apply it over and over, in exactly the proper place upon the fabric, until the entire surface had been covered with the design. Of course a separate block, with the proper portion of the design thereon, was reqnirerl for each color, and between the applications of two suc- cessive colors the cloth was thoroughly dried. The Perroiine (so called from the name of its inventor) is a device for producing block print- ing by machinery. The design is engraved in relief upon cast metal plates. It is now but lit- tle used. The invention of the roller printing press marked an epoch in the history of textile print- ing. It made possible the production of pat- terns complicated in design and coloring, at a cost so slight as to make it practicable to use them for the mo.st inexpensive fabrics. The first patents for roller printing were taken out in England in 1743 and 1772, and in France in 1801. The invention is usually ascribed to Thomas Bell. The roller printing press consists of a huge cylinder or bowl, revolving on its axis and carrying the cloth to be printed. While passing over this drum the material to lie printed is brought into contact with another cylinder which carries the color and upon whose surface the pattern is engraved. The drum is covered or cushioned with several layers of a coarse cloth called lapping. Against this bowl is pressed the engraved copper cylinder, which receives the color from a wooden cylinder, covered with cloth and dip- ping into the color-trough. In order to remove the surplus color from the copper roller, the so-called doctor is applied; this is simply a, sharp blade which is pressed at an angle on the roller and scrapes the surplus color from it. In order to remove any loose threads or fila- ments, there is also a lint-doctor. The cloth to be printed passes between the engraved cop- per roller and the bowl, and in order to have an elastic underlayer it is supplied with a llanket, which is usually of wool. To keep the blanket clean the hack-cloth, of unbleached cot- ton, is allowed to intervene between blanket and printing cloth. The three cloths (blanket, back- cloth, and cloth to be printed) go through at the same time between the howl and the print- ing roller. The latter gives the color kept in the engraving over to the printing cloth next to it. This giving up is caused ( 1 ) by the pressure of the printing roller against the drum, and (2) by the action of the lapping and blanket, which, by forming a kind of elastic cushion, press the cloth into the engraved cavities of the roller and force the cloth to absorb the color, which is prevented from spreading by the pressure exerted at the same time. The copper roller is a hollow cylinder mounted on an iron man- drel. It is sometimes engraved by hand, but more often by machine. The engraving is ac- complished mechanically by producing the de- sign in a small section by hand, then reproduc- ing it on a second piece of hardened steel, from which it is easily stamped over and over on the comparatively soft copper. By another method, known as the clicniical process, the copper roller is covered with varnish through which the pat- tern is cut with a pantograph (q.v.). The roller is then immersed in acid, which eats out the ex- posed copper in the form of the design, after which the varnish is removed from the roller. The printed fabric is dried by passing it slowly over and near a series of steam-heated hollow cast-iron plates. As each roller prints but one color, there are as many rollers in a cylinder printing press as the desired number of colors. Great care has to be observed to keep the (T'olors clear. In order that a dark shade may not soil a light one, the lighter shades are usually printed first and sometimes a plain starch roller is applied between the two. Before it is printed the cloth is subjected to various preliminary processes, depending upon the nature of the fabric. Cotton goods are bleached and padded or treated to dressing to give them the proper body and surface. They are then run through the lint-doctor to remove all hairy projections, ^^'oolen goods must be treated to a preliminary bath in a weak solu- tion of sodium hypochlorite. The cloth is moist- ened before printing, and after printing is washed and dried. Silk has to be prepared for printing by suitable agents, such as tin with or without an acid. Both wool and silk require to be entirely freed from grease before they can be printed. The preparation of the colors for printing re- quires great skill and knowledge of the proper- ties of the different dyestuffs. The colors are mixed in copper pans so mounted that their contents can be boiled by steam, cooled with water, and easily emptied. Wooden paddles are provided for stirring the colors, or the agitation may be performed by mechanical appliances. As most of the colors are thickened with starch or flour, so that they will spread well, they re- quire straining through a copper wire sieve. The printing of cotton fabrics is a much more complicated and difficult process than that of printing silk or wool, because many of the com- plex methods that may be applied to the former are. from the nature of the material, inappli- cable to the latter. The many different methods and combinations of methods by which the color effects are produced on cotton fabrics have been variously classified by writers on textile print- ing. To understand the production of these different so-called 'styles' involves a knowl- edge of the principles and chemistry of dyeing. (See Dyeixg.) The simplest classification is that adopted by Georgievic, in his work named in the bibliography. According to his classifica- tion, the production of a pattern upon cot- ton cloth may be accomplished as follows: (1) Direct printing; (2) combined dyeing and printing; (3) discharge style printing; (4) re- serve style printing. Direct printing is done by mixing the desired color with the proper fixing agents and applying the mixture directly to the fabric. In combined di/eiiig and printing, the printing is done with mordants, and then the whole fabric is dyed. In the discharge style the effect is produced either by using a solution that will discharge the mordant or the dye itself. In the rexrrvc sljile various substances, printed on the fabric, are employed to prevent absorp-