Various antiseptics are employed for the preservation of flour paste, mucilage, etc. Boric and salicylic acids, oil of cloves, oil of sassafras, and solution of formaldehyde are among those which have given best service. A durable starch paste is produced by adding some borax to the water used in making it. A paste from 10 parts (weight) starch to 100 parts (weight) water with 1 per cent borax added will keep many weeks, while without this addition it will sour after six days. In the case of a gluing material prepared from starch paste and joiners' glue, borax has also demonstrated its preserving qualities. The solution is made by mixing 10 parts (weight) starch into a paste with water and adding 10 parts (weight) glue soaked in water to the hot solution; the addition of 1/10 part (weight) of borax to the solution will cause it to keep for weeks. It is equal to the best glue, but should be warmed and stirred before use.

Board-Sizing

A cheap sizing for rough, weather-beaten boards may be made by dissolving shellac in sal soda and adding some heavy-bodied pigment. This size will stick to grease spots. Linseed oil may be added if desired. Lime-water and linseed oil make a good heavy sizing, but hard to spread. They are usually used half and half, though these proportions may be varied somewhat.

Rice Paste

Mix the rice flour with cold water, and boil it over a gentle fire until it thickens. This paste is quite white and becomes transparent on drying. It is very adherent and of great use for many purposes.

Casein Paste

A solution of tannin, prepared from a bark or from commercial tannin, is precipitated with lime-water, the lime being added until the

solution just turns red litmus paper blue.

The supernatant liquid is then decanted,

and the precipitate is dried without artificial heat. The resulting calcium tannate is then mixed, according to the purpose for which the adhesive is intended, with from 1 to 10 times its weight of dry casein by grinding in a mill. The adhesive compound is soluble in water, petroleum, oils, and carbon bisulphide. It is very strong, and is applied in the form of a paste with water.