A common and good CEMENT FOR PORCELIAN OR GLASS is made as follows:—
| Calcined gypsum or plaster of Paris | 50 |
| Calcined lime | 10 |
| White of egg | 20 |
This must be quickly mingled and rapidly used, as it sets very rapidly and becomes extremely hard. It makes an admirable bed for mosaics or ceresa.
When plaster of Paris is simply combined with burnt alum in water, the objects mended with it require several weeks to set or adhere. Gypsum combined with gum alone holds firmly, but does not resist water (vide General Recipes).
Cements for luting or closing chemical apparatus:—
| Dried clay | 10 |
| Linseed-oil | 1 |
This endures heat to boiling-point of quicksilver.
A more resistant fireproof is as follows:—
| Manganese | 10 |
| Grey oxide of zinc | 20 |
| Clay | 40 |
| Linseed-oil varnish | 7 |
Of the oil only so much is needed as to combine the mass to a paste.