Alan Summerly Cole

“ The art of making colours for textile-printing demands both chemical knowledge and extensive technical experience, for their ingredients must not only be properly proportioned to each other, but they must be specially chosen and compounded for the particular style of work in hand. For a pattern containing only one colour any mixture whatever may be used so long as it fulfils all conditions as to shade, quality and fastness ”

“ A further and most important appliance is the “doctor”—a thin sharp blade of steel which rests on the engraved roller and serves to scrape off every vestige of superfluous colour from its surface, leaving only that which rests in the engraving. On the perfect action of this “doctor” depends the entire success of printing, and as its sharpness and angle of inclination to the copper roller varies with the styles of work in hand it requires an expert to “get it up” (sharpen it) properly and considerable practical experience to know exactly what qualities it should possess in any given case. ”

“ Roughly speaking, the operation of engraving is performed by three different methods, viz. (1) By hand with a graver which cuts the metal away; (2) by etching, in which the pattern is dissolved out in nitric acid; and (3) by machine, in which the pattern is simply indented.
(1) Engraving by hand is the oldest and most obvious method of engraving, but is the least used at the present time on account of its slowness. The design is transferred to the roller from an oil colour tracing and then merely cut out with a steel graver, prismatic in section, and sharpened to a bevelled point. ”

“ Sonping is also an important factor in the production of the best work. It clears the white parts of the goods, brightens the colours and generally improves the whole appearance of the cloth. The strength and temperature of the soap solution, the duration of the soaping and the type of machine used are all varied according to the fastness of the colours to be soaped. As in washing, the alizarine dyed colours, alizarine “ steam " reds and pinks, aniline black and the ice-colours, will not only withstand a long, hot and strong soaping, but are greatly brightened and enhanced in beauty thereby. ”

“ Block-printing by hand is a slow process: it is, however, capable of yielding highly artistic results, some of which are unobtainable by any other means, and it is, therefore, still largely practised for the highest class of work in certain styles. ”

“ Silk is especially adapted to discharge and reserve effects. Most of the acid dyes can be discharged in the same way as when they are dyed on wool; and reserved effects are produced by printing mechanical resists, such as waxes and fats, on the cloth and then dyeing it up in cold dye-liquor. The great affinity of the silk fibre for basic and acid dye-stuffs enables it to extract colouring matter from cold solutions, and permanently combine with it to form an insoluble lake. ”

“ In Schlieper and Baum's process (also known as the glucose process) the cloth is first prepared in glucose, and then printed with a colour containing finely ground indigo, caustic soda and dextrine thickening (also made with caustic soda) . After printing, the cloth is “aged,” that is, passed through damp steam for a few minutes to effect the reduction and solution of the indigo, and is then hung up in a cool chamber for a day or two, in order to re-oxidize the indigo-white to indigo by the action of the oxygen in the air. ”

“ In rare instances of middle-age Moorish or Arabian fabrics the gold threads are made with strips of parchment or paper gilt and still rarer are instances of the use of real gold wire.
In India the preparation of varieties of gold and silver threads is an ancient and important art. The “gold wire” of the manufacturer has been and is as a rule silver wire gilt, the silver wire being, of course, composed of pure silver. The wire is drawn by means of simple draw-plates, with rude and simple appliances, from rounded bars of silver, or gold-plated silver, as the case may be. ”

“ The darkest qualities are very useful for strongly acid colours, and with the exception of gum senegal, are the best for strongly alkaline colours and discharges. Like the natural gums, neither light nor dark British gums penetrate into the fibre of the cloth so deeply as pure starch or flour, and are therefore unsuitable for very dark strong colours. ”

“ Mordant colours like logwood black are applied in the usual way. The printing of wool is carried out exactly as for cotton, but if the best results are to be obtained, the engraving of the rollers must be deep, the blanket on the machine as solt as possible, and the drying of the printed cloth very gentle. After printing, the goods are steamed in moist steam or wrapped between moistened “gre-ys" and steamed in a "cottage" steamer. If too little moisture is given, the colours lack both strength and brilliancy; if too much they run. ”

“ Aniline black is formed by the oxidation of aniline.
As a rule the oxidation of the aniline is brought about by means of sodium chlorate in presence of suitable oxygen carriers such as copper sulphide, vanadium chloride or potassium ferrocyanide. Copper and vanadium blacks are usually developed after printing by being aged in a moderately warm room for a day or two, when they become converted into “emeraldine,” at which stage they are taken down, and passed through a hot solution of bichromate of potash to complete the oxidation of the aniline. ”

“ The necessity for “ ties " exercises great influence on the design, and in the hands of a designer of indifferent ability they may be very unsightly. On the other hand, a capable man utilizes them to supply the drawing, and when thus treated they form an integral part of the pattern and enhance its artistic value whilst complying with the conditions and the process.
For single-colour work a stencilling machine was patented in 1894 by S. H. Sharp. It consists of an endless stencil plate of thin sheet steel which passes continuously over a revolving cast iron cylinder. ”

“ In the 14th century the making of satins heavily brocaded with gold threads was associated conspicuously with such Italian towns as Lucca, Genoa, Venice and Florence. Fig. 4 is from a piece of 14th-century dark-blue satin broached in relief with gold thread in a design the like of which appears in the background of Orcagna’s “Coronation of the Virgin,” now in the National Gallery, London. During the 17th century Genoa, Florence and Lyons vied with each other in making brocades in which the enrichments were as frequently of coloured silks as of gold intermixed with silken threads. ”

“ As a rule the colouring matter is beaten up into a smooth paste with the necessary quantity of a strong solution of albumen and then reduced to its proper strength by the addition of tragacanth mucilage or starch paste. The main factor in the successful working of pigment colours is their fineness of division; the finer they are the better they print and the more beautiful is their quality of colour. ”

“ The mode of printing is almost self-evident; the roller C revolving in the direction of the arrow takes colour from the “ furnish er ” F, the excess is scraped off by the “ doctor ” G and, in continuing its Course, it comes in contact with the cloth K, which being pressed by the cylinder A into the engraving abstracts the colour therefrom and of course receives an exact impression of the engraved pattern. Larger machines printing from two to sixteen colours are precisely similar in principle to the above, but differ somewhat in detail and are naturally more complex and difficult to operate. ”

“ Before printing it is very essential to strain or sieve all colours in order to free them from lumps, fine sand, &c., which would inevitably damage the highly olished surface of the engraved rollers and result in bad printing. livery scratch on the surface of a roller prints a fine line in the cloth, and too much care, therefore, cannot be taken to remove, as far as possible, all grit and other hard particles from every colour. The straining is usually done by squeezing the colour through fine cotton or silk cloths. ”

“ For certain classes of work the “perrotine” possesses great advantages over the hand-block; for not only is the rate of production greatly increased, but the joining up of the various impressions to each other is much more exact—in fact, as a rule, no sign of a break in continuity of line can be noticed in well-executed work. ”

“ If they are too coarse they give rise to innumerable defects, either by sticking in the engraving or by scratching the roller, or, if they print at all, by yielding uneven masses of colour, granular and speckled in appearance and quite unsaleable. Even when finally ground they are liable to clog the engraving of the rollers-a defect which is more or less successfully overcome by replacing the colour-furnishing roller in the printing machine by a revolving brush. ”

“ The small quantities of ammonia, turpentine, glycerin and oil are added to prevent the colour from frothing during the printing process.
Chrome yellows and oranges are frequently mixed with a little cadmium nitrate to counteract the action of sulphuretted hydrogen on the lead salts.
The great disadvantage of pigment colours is that although extremely fast to light and soap they are liable to rub off, if the fabric is subjected to much friction in washing. ”

“ Unlike cotton, however, wool requires to be specially prepared, after bleaching, if the full tinctorial value of the colours is to be obtained.
Two quite different methods of preparation are resorted to, namely (1) the chlorination of the wool; and (2) the precipitation of stannic acid on the fibre. In the first method the woollen fabric is first passed through a solution of bleaching powder, then well squeezed and passed, without washing, into dilute sulphuric or hydrochloric acid, squeezed again and well washed in water, after which it is dried. ”

“ The printing roller C is the only part of the machine directly connected with the motor or main drive of the works through the cog-wheel on its axlethe “ mandril ”-all the other parts deriving their motion from it, either by friction as in the case of the cylinder or by a spur wheel as in that of the colour-furnishing roller. ”

“ The “cover and pad” style is, for the most part, restricted to dyed alizarine purples under which red, black, dark purple and white can all be reserved at the same time, thus giving rise to very pleasing effects. For example: white cloth is first printed with four “colours,” viz., citrate of soda and citric acid for the white; logwood and iron for the black; strong iron mordant for the purple; and aluminium acetate at 6° Tw. with 8 oz. per gallon of stannous chloride for the red. (The stannous chloride acts as a resist for iron mordants.) ”

“ The copper roller is mounted on a stout steel axle, at one end of which a cog-wheel is fixed to gear with the driving wheel of the machine, and at the other end a smaller cog-wheel to drive the colour-furnish in roller. The cast iron pressure cylinder is wrapped with several thicknesses of a special material made of wool and cotton—lapping—the object of which is to provide the elasticity necessary to enable it to properly force the cloth to be printed into the lines of engraving. ”

“ Print the white and yellow, dry, dye in the indigo vat-sour slightly in sulphuric acid, wash, and pass into a hot solution of bichromate of soda, which develops the lead yellow. Reserve whites also contain lead salts when used for white alone, but obviously the white given is best suited to white and yellow reserves, as its soluble copper salts wash out before the “chroming” stage is reached.
(f) Reserves under Sulphur Colours.-These are obtained with zine chloride. They are not much used, but are capable of yielding fine effects. ”

“ After steaming, the printed goods are washed in plenty of water, then dried up and. finished with a little glycerin or some waxy preparation.
Discharges may be very easily obtained on wool dyed in acid dye-stuffs, by means of stannous chloride and basic colours for the coloured effect, and hydrosulphite for the white.
Silk-Printing.
Silk-printing calls for no special mention. The colours and methods employed are the same as for wool, except that in the case of silk no preparation of the material is required before printing and the ordinary dry “steaming” is preferable to damp “steaming.” ”