A quart of water is put in the crock and heated to boiling; it is then taken off the open fire and two pounds of the finest gelatine stirred in, a little at a time. After the gelatine is completely dissolved there is to be added eight or ten pounds (according to the quality of the gelatine) of the finest white sirup previously warmed, and constantly stirred. The mass must not boil, as it would easily burn, or turn brown and acquire a bad color.
Thirty or forty pounds of a beautiful white elastic mass can be made by this recipe in an hour at a cost of ten or twelve cents. Its chief use is for making figures and ornaments to put on bridal cakes and other fanciful productions of the confectioner. It contains no harmful ingredients and can be eaten without danger. If coloring is added, cochineal, plant green (chlorophyl), and turmeric are safer than aniline colors.
CAOUTCHOUC.
A. Levy contributes the following brief account of this subject to the Moniteur Scientifique:
The crude gum cut in irregular strips is passed five or six times between two strong rolls sixteen inches in diameter, and making two or three revolutions per minute. These rolls are kept wet by water trickling on them. This broad strip of gum is perforated with foreign substances and looks like a sieve. It is next put in the cutting machine, a horizontal drum provided with an axle having knives on it. So much heat is produced by this cutting that the water would soon boil if it were not renewed. A second machine of this kind completes the cutting and subdividing, and expels the air and water from it. The mass is then pressed in round or quadrangular blocks.
The vulcanization of thin articles from one twenty-fifth to one-sixteenth inch thick, is done by Parkes' patented process, that is, dipping it in carbon disulphide for a short time, to which chloride or bromide of sulphur has been added, and when the solvent has evaporated the sulphur remains behind. Balls, ornamental articles, and surgical apparatus are dipped into melted sulphur at 275° or 300° Fahr.
The third most important process consists in mixing in the sulphur mechanically with the gum in the cutting machine.
After the pieces have received the form they are to have they are heated with steam or hot air to 275°. Flat articles are vulcanized between press plates heated by steam. This vulcanization is said to have been discovered accidentally by searching different colored stuffs, some of which were dyed yellow with sulphur; the latter stood well.