Tragacanth, or gum tragacanth, exudes from Astragalus verus, a tree indigenous to Asia. The term gum is a misnomer, as tragacanth does not actually dissolve in water nor in spirit of wine, but merely swells up in water to a soft gelatinous mass. Tragacanth consists of irregular pieces of a pure white to yellowish color. It is chiefly used for confectioner’s purposes, though sometimes as a paste for fancy articles. This variety of gum is found, together with arabine, in the gum which exudes from cherry, plum, almond, and apricot trees, and gives the mucilaginous character to the watery decoctions prepared from certain seeds, such as linseed and quince-seed, and from the root of marshmallow.
PASTES AND MUCILAGES FOR SPECIAL PURPOSES.
Starch paste. Corn starch 8 ozs., cold water ½ pint, boiling water 1 gallon.
Beat up the starch in the cold water until reduced to a creamy consistence, then pour the mixture into the boiling water and stir briskly until the white, semi-opaque mass, becomes transparent. Should it fail to do so, place it over the fire, and boil until the desired result is obtained, stirring constantly.
Flour paste. Wheat flour 4 lbs., cold water 2 quarts, alum 2 ozs., hot water ½ pint, boiling water 2 gallons.
Work the wheat flour into a batter free from lumps with the cold water. Dissolve the alum in the hot water. Then stir the batter into the boiling water, and if necessary, continue boiling until the paste thickens into a semi-transparent mucilage, after which stir in the alum solution. This makes a very fine paste for wall-paper.
Strong adhesive paste. Rye flour 2 lbs., cold water 1 quart, boiling water 3 quarts, pulverized rosin 1 oz.
Make the flour into a batter with the cold water, free from lumps, and pour into the boiling water. Boil, if necessary, and while hot stir in the pulverized rosin, a little at a time. This paste is very strong, and will fasten heavy wall-paper or thin leather. If too thick, thin with hot water. Never thin paste with cold water.
Paste that will not sour. Allow 4 parts by weight of glue to soften in 15 parts of cold water for some hours, and then heat moderately till the solution becomes quite clear; then add, while stirring, 65 parts of boiling water. In another vessel stir up 30 parts of starch paste with 20 parts of cold water, so that a thin, milky fluid without lumps is obtained. Into this pour the boiling glue solution, stirring constantly, and keep the whole at the boiling temperature. After cooling, add 5 to 10 drops of carbolic acid to the paste. Preserve the paste in closed bottles to prevent evaporation of the water. It will thus keep good for years.
Venetian paste. White or fish glue 4 ozs., cold water ½ pint, Venice turpentine 2 fluid ozs., rye flour 1 lb., cold water 1 pint, boiling water 2 quarts.