Large quantities of isinglass and gelatine, specially prepared for the purpose, are used for clarifying and fining beer, wine and other liquids, as well as for preparing jellies. The material to be used for jellies and other culinary purposes must, of course, be colorless and entirely free from odor. Jellies are made palatable by flavoring with spices, sugar, essences, etc., before congealing, A vegetable gelatine, Agar-Agar, which will be referred to later on is now brought from China, and being cheaper and perfectly free from odor, has become quite a competitor with isinglass and gelatine.
Prior to the introduction of Liebig’s and other beef extracts, bouillon tablets, consisting of a mixture of bone-jelly, meat broth, extract of pot herbs and flour, were largely used. One hundred and ten pounds of meat repeatedly boiled yield five pounds of bouillon tablets. A good meat broth, though not equal to that from Liebig’s or other meat extracts, is obtained from these tablets by the addition of thirty times their weight of water.
If glue be dissolved in water, it gelatinizes at the ordinary temperature, and if the solution be mixed with other fluids, for instance, meat broth, fruit juices and essences, which in the form of jelly are to serve as food, it effects their solidification.
Glue acts as a healing agent by preventing the access of air to wounds. Court plaster is prepared from gelatine. When cabinet-makers cut themselves, they apply glue to the wound with the best success. In hospitals a compound of gelatine and glycerine is used as the best means of closing wounds, the same compound having also been successfully used for preserving articles of food such as eggs, fruit, and even meat.
Every good quality of glue can be used for the above purposes.
Medicines of a disagreeable taste are frequently inclosed in gelatine capsules, so that they can be taken without causing inconvenience to the patient. The use of these capsules has grown to such an extent as to form a special branch of industry. The mode of manufacturing them will be described later on.
Glue for elastic masses and as a partial substitute for rubber. Glue mixed with glycerine forms an elastic mass resembling rubber. The same effect can be produced by an addition of molasses. This elastic mass, the preparation of which will be described later on, is of great importance for the manufacture of printers’ rollers, for moulds, etc. Some manufacturers prepare the mass ready for use, so that the printer or lithographer need only remelt it, and cast it in a mould.
Glue is of great importance in photolithography as, mixed with chromium salts, it is the only known means of transferring a photographic negative to the stone. In photography, gelatine is used for negative pictures upon glass. For the manufacturer of casts of plaster of Paris or cement, this glue mass, which is generally used without an addition of glycerine, is indispensable for making moulds which are much undercut.
Glue mixed with glycerine may be used as a substitute for rubber in manufacturing elastic toys, such as dolls’ heads, animals, etc. For these purposes it is advisable to select glue which forms a very solid jelly, even if it possesses but little adhesive power, pure bone-glue being the best.
Glue mixed with glycerine (1 part glue, 1 part glycerine) is used as hectograph mass for the transfer of matter written with concentrated solution of aniline color.