With dyeing is often associated the art of “scouring,” for a knowledge of the properties of the dye-stuffs used enables the workman to discriminate between what will brighten and what would injure the goods to be cleaned.
CALENDERING.
The process of calendering is resorted to for producing a fine smooth surface on calicoes and other goods, and for rendering them sufficiently even to be printed upon (see “[Calico-printing”]). The calendering machine consists of a set of five rollers, constructed to revolve at unequal rates, so that the one which turns upon the face of the calico not only rolls it between itself and its fellow, but—turning faster—rubs it and gives a gloss to the surface similar to the effect which would be produced if the goods were laid on a table, and the roller rubbed over them instead of being rolled. These rollers are very curiously constructed. They are made by packing many hundreds of round pieces of pasteboard—having each a square hole in the centre, and several smaller circular ones in the margin—on to a central bar of iron, with similar bars through the smaller holes, until a sufficient number have been added to produce the length of roller required. Nuts are then fitted to the ends of the smaller iron bars, and these being screwed tightly, compress the whole into so solid a mass, that it can be turned in a lathe to a perfectly smooth surface, which is (unlike wood) not liable to crack, and, being slightly elastic, does not crush the goods, as metal rollers would.
BREAD MAKING.
This process is much the same whatever kind of meal or flour may be used, whether wheaten, barley, &c. A certain portion of the flour is mixed with warm water (in which a little salt is generally dissolved), some yeast or “barm” (the froth from the fermentation of beer) is added, and the whole worked together to a pasty consistence, this is put into a pan to keep warm, and is called “the sponge;” besides flour and water nearly every baker mixes his sponge with a certain proportion of potatoes boiled to a “squash,” and passed through a sieve to separate the rinds. In an hour or so it swells up to double its original size, from the fermentation which is going on producing a kind of gas called “carbonic acid,” which being formed in every part of the “sponge,” inflates it to a great extent. After a time it sinks down (most of the gas escaping), and begins to rise again; it is then mixed with the remainder of the flour (and some water if necessary), and the whole thoroughly kneaded together with the hands till it is all of an equal consistence—this should be neither too stiff, nor so soft as to stick to the hands. It is now to be cut up and weighed out into pieces to form each loaf. The oven in which the bread is baked is made of “fire-brick,” and so embedded in earth or brickwork that when heated it shall not readily cool; this is heated with coal or wood till it is nearly red-hot and the loaves are put in and left till baked.
SUGAR REFINING.
When brown or raw sugar is refined it forms the white crystalline product known as loaf sugar. The process involves many ingenious arrangements in its detail, but the essential object to be obtained is the separation of all coloring matter from the raw material without producing any more by the process, which is a greater difficulty than would at first appear, for all solutions of sugar evaporated in the open air become to a great extent colored, and the longer the exposure, and the higher the temperature, the worse the product; a substance forming called “caramel,” which discolors it.