®54

DYEING AND CALICO PRINTING.

circumstance that the irregular abrasion of different parts of its surface rendersthe attainment of a really level shade impossible.

One of the subsidiary operations applied to stuffs about to be dyed in thepiece is singeing. The objed of this process is the entire removal of allroughnesses and projecting fibres, so that the stuff may exhibit a perfectlysmooth surface. This can only be effected by a rapid combustion, so perfectlyunder control that the down may be entirely burnt away without the body ofthe tissue being in the slightest degree weakened or discoloured. This wasformerly done by passing the goods with great velocity over a convex plate ofcast-iron, heated to a very high temperature. It is now executed, in preference,by the aid of burning coal-gas. One of the best arrangements for this isTulpin’s singeing-machine (PI. VIII.). The use of gas was at first greatlyrestricted, in consequence of a defect which seemed insurmountable. As thepieces moved above the points of the flames which burnt the down, the adionwas not sufficiently limited to the surface, but extended to the filaments in theinterior of the tissue, which was thus rendered thinner, and its value wasreduced. Tulpin remedies this defed by employing, not the point of theflame, but its lateral part, along which he causes the stuffs to graze. Hismachine is so contrived that the operation can, at will, be repeated twice oneach side. The steadiness of the flame is secured by means of a ventilatorwhich draws off the produdts of combustion. A smaller ventilator sends inair, and mixes it with the coal-gas in sufficient proportion to produce a blueflame as in the Bunsen burner, giving out heat rather than light, and com-pletely free from smoke. In this manner the danger of staining or blackeningthe pieces is completely obviated. This singeing-machine may be advanta-geously used in preparing calico for printing.

Another important operation is “ crabbing.” Before stuffs can be dyed, alldirt, grease, and the dressing used by the weaver, must be completely removed.The pieces are generally first passed through hot water, to dissolve and removesize or stiffening. They are next treated with hot lyes of soap, carbonate ofsoda, and liquid ammonia, to remove all fatty and resinous matters. Everytrace of soap and alkali is finally washed out, by rinsing in abundance ofwater. The apparatus used resembles that figured on p. 306 (Fig. 22).

The manipulation—“ working or turning ”—during the ad of dyeing itselfis conducted in different manners, according to the nature of the goods. Inwool- and rag-dyeing the dyer’s pole is still employed to turn the materialoperated upon ; but in piece-dyeing there is fixed over every beck or cistern aroller or wince, which can be turned by hand, or, as is more common in largemodern establishments, by steam- or water-power. Round this roller thepieces are wound, and, as it revolves, they are alternately let down into theliquid and drawn out again, the dyer taking care that they do not get entangled,

■—which sometimes happens with thin goods,—and that they coil and uncoilevenly.

A'fter the completion of the dyeing—properly so-called—the pieces are, as arule, saturated with an excess of uncombined colouring matter, from whichthey require to be freed by copious washing. This was formerly effeded bysuspending the goods in a clear running stream. Since in manufaduringdistrids the rivers are now more adapted to soil than to cleanse anything,this primitive method of washing has given place to mechanical arrangements