20 lb. clean river sand, 2 lb. litharge, 1 lb. quicklime, sufficient linseed-oil to form a thin paste. Used for joining fragments of stone.
Gad's. 3 parts well-dried and powdered clay, 1 of iron oxide, mixed together and made into a stiff paste with boiled oil. Used for work required to harden under water.
For grotto work. Commonest sealing-wax.
An excellent cement for foot-walks, and for all uses which require exposure to the weather or to dampness, is described in 'Der Praktische Maschinen-Constructeur.' It is made by thoroughly stirring Portland cement or good hydraulic lime into a warm solution of glue, so as to make a thick paste, and applying it immediately. In three days it acquires extraordinary hardness and tenacity. It is an excellent cement for joining the porcelain heads to the metal spikes which are used as ornamental nails.
Fahnejelm recommends a mixture of 75 parts of carefully washed chalk and 25 parts of washed kaolin, to be first calcined to red heat, and afterwards ground. The powder is then snow white, or, if the heat has been too great, it has a bluish shade. Either alone, or with a small percentage of gypsum, it makes an excellent hydraulic cement.
1 part yellow Botany Bay gum, 1 of brickdust, melted together. For stoneware.
60 parts chalk, 20 of lime, 20 of salt, 10 of Barnsey sand, 5 of iron filings, 5 of clay; ground together, and calcined. Beale's.
3 parts clay, 1 of slaked lime; mixed, exposed for 3 hours to full red heat, and ground to powder. Bruyere's hydraulic.