ivory, artificial

Значение термина ivory, artificial в knolik

• Make isinglass and brandy into a paste, with powdered egg-shell, very finely ground. Give it any desired colour; oil the mould, into which the paste must be poured warm. Leave the paste in the mould until dry, when its appearance strongly resembles ivory.
• In making articles of artificial ivory, the greatest difficulty hitherto has been that in order to gain the necessary firmness, a large percentage of the binding substance had to be used, and hence only dark coloured articles could be produced. Hyatt, however, produced a substance having a pure white colour. This result is arrived at by grinding up any suitable inert matter with a solution of a proper cement. The cement solution is then expressed, the residue is dried and ground, and the powder thus obtained is heated and pressed into moulds. The most suitable inert matter found is oxide of zinc, and the best cement is shellac, or some other similar vegetable substance. A solution of NH₃ forms the solvent: Hyatt first dissolves 8 parts shellac in 32 parts NH₃, sp. gr. 0.995, by thoroughly mixing the two at a temperature of 99° F. (37½° C.) for 5 hours in a rotating cylinder. 40 parts of oxide of zinc are now mixed by hand into the thin syrupy solution, and the mixture is well ground in a colour-mill. The NH₃, having served its purpose, is now driven off by heat, or by exposing the mixture on glass plates for a long time to the air. The residue consisting merely of dry shellac and zinc oxide, is again finely powdered, and the powder thus obtained is pressed into the moulds with a pressure of about 2000 lb. per sq. in., and at a temperature of 275° to 210° F. (125° to 137½° C.). If the article is to be coloured, the colour is added either to the solution just before the first grinding, or the dry mass before the second grinding.

Рядом со словом ivory, artificial в knolik