_The Calico-Printers' mordant or base of alum for yellow and red goods, either for printing or dyeing; and on compound colours._ Take one gallon of soft and pure water, of a heat of 150°, three pounds of common alum, one pound and a half of sugar (acetate) of lead; mix these together, and let them stand for two or three days, so that they may incorporate, often stirring them during that interval; then add two ounces of pearl-ash, and the same quantity of clean powdered chalk or whiting. After a time the clear liquor, now become _an acetate of alum_, must be drawn off. When used, it is thickened either with paste, flour, or gum arabic, or senegal; four pounds of either of the gums to each gallon of liquor[5]. A block or a press similar to a copper-plate press for paper, but much larger, and having the copper plates in proportion, is employed to spread the acetate of alum from a utensil called a sieve, which is, however, not porous, while a boy or girl called a _Teerer_, works it smooth; when smooth on the sieve, the printer applies his block, and charges it with the acetate of alum; the block thus charged, is correctly put on the cotton cloth, which is laid upon a blanket spread upon a table; it is then struck with a mallet once or twice, by which, or by the pressure of the rolling-press, if copper-plate, the acetate of alum is driven into the pores of the cloth. The cloth thus prepared, is hung up in a hot stove, and dried by a high degree of heat. The goods are now ready, if for _red_, for the _madder_; and if for _yellow_, for the _weld_ copper. Sometimes, however, lately, the colour is previously prepared, and applied at once in more instances than are prudent. To the above mordant, _M'Kernan_ adds three ounces of _sulphate of copper_, omitting the potash; and he adds, "When the colour is wanting on the scarlet cast, omit the sulphate of copper." Wool readily takes the alum at a boiling heat; _common alum_ is in many instances proper for wool; and in others, where it might be improper, it is corrected by the use of argol or cream of tartar. _Yellow_ and _red_ produce _orange_; _red_ and _blue_, _purple_; but upon _cotton_, a scarlet, purple, or crimson cannot be produced in any way equal to those colours in wool or silk. _Yellow_ and _blue_ form the _green_. _On Bleaching Linen, Cotton, &c._ We cannot enter with much minuteness into this part of the subject, more especially as the _art of bleaching_ is usually a separate one from that of _dyeing_. Yet as in fact the arts of _dyeing_ and of _bleaching_ depend in a great degree on the same principles, some notice of bleaching, in a treatise on dyeing, seems absolutely necessary.