The Boot and Shoe Manufacturers' Assistant and Guide. / Containing a Brief History of the Trade. History of India-rubber and Gutta-percha, and Their Application to the Manufacture of Boots and Shoes. Full Instructions in the Art, With Diagrams and Scales, Etc., Etc. Vulcanization and Sulphurization, English and American Patents. With an Elaborate Treatise on Tanning.

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OF GLUE.

To prepare glue, it must be steeped for a number of hours, over night, for instance, in cold water, by which means it will become considerably swelled and softened. It must then be gently boiled, till it is entirely dissolved, and of a consistence not too thick to be easily brushed over wood.

When glue, by repeatedly heating it, has become of a dark and almost black color, its qualities are impaired; when newly melted, it is of a light ruddy brown color, nearly like that of the dry cake held up to the light; and while this color remains, it may be considered fit for almost every purpose. Though glue which has been melted is the most suitable for use, other circumstances being the same, yet that which has been the longest manufactured is the best. To try the goodness of glue, steep a piece three or four days in cold water; if it swell considerably without melting, and when taken out resumes, in a short time, its former dryness, it is excellent. If it be soluble in cold water, it is a proof that it wants strength.

A glue which does not dissolve in water, may be obtained by melting a common glue with the smallest possible quantity of water, and adding by degrees linseed oil rendered drying by boiling it with litharge; while the oil is added, the ingredients must be well stirred to incorporate them thoroughly.

A glue which will resist water, in a considerable degree, is made by dissolving common glue in skimmed milk.

Finely lixiviated chalk added to the common solution of glue in water, constitutes an addition that strengthens it, and renders it suitable for boards, or other things which must stand the weather.

A glue that will hold against fire or water, may be prepared by mixing a handful of quick-lime with four ounces of linseed oil: thoroughly lixiviate the mixture, boil it to a good thickness, and then spread it on tin plates in the shade; it will become exceedingly hard, but may be dissolved over a fire, as ordinary glue, and is then fit for use.