Читать книгу A Manual of Mending and Repairing; With Diagrams онлайн

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To make the best flour-paste, flour should be kneaded in a bag under water till all the starch is washed away. What remains is a substance closely allied to caseine, or the white of egg. Combined with lime it forms a hard cement. A very slight admixture of carbolic acid (also oil of cloves) will keep paste from souring or decay. This acid has the property of destroying the growth of the minute vegetation which constitutes fermentation, just as other strong scents or perfumes are supposed to disinfect rooms, &c.

A very great number of other ingredients, such as the oxides of lead or zinc, manganese, baryta, sulphur, sal ammoniac, flint-sand, clay, salt, ochre, varnish, galbanum, or frankincense, enter into certain recipes, but those already given may be regarded as constituting by far the principal portion of all cements in ordinary use.

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Fictile or Ceramic ware embraces, roughly speaking, all that is made of clay, or mineral bases or materials, and which is subsequently baked to give it hardness. The better the material and the more intense the heat, or the greater the number of bakings to which most kinds are subjected, the harder and more lasting will they be. The old china ware which preceded porcelain, a great many specimens of old Roman vessels, and, for a more modern example, old Italian majolica and Hungarian wine-pitchers, made all within a century, are as hard as stone. They chip a great deal before they break, just as agate might do.