A very good cement for mending, especially where the objects are exposed to water, whether they be of stone or earthenware, is made as follows:—
| Powdered glass | 40 |
| Washed litharge | 40 |
| Linseed-oil varnish | 20 |
The powdered glass is prepared by heating glass red-hot, casting it into water, grinding and sifting it. This powder is saturated with the linseed-oil varnish, and heated in a kettle. This cement sets hard in three days. Lehner observes that glass-powder serves in such recipes to resist the action of acids, &c., since it forms in combination on the surface a glaze of great hardness; that is, the glass and lead form a chemical combination. Pulverised calcined glass therefore acts not as an “indifferent” but as a chemical ingredient.
Caseine, or Cheese, forms the basis of several recipes for mending stone, as when there are holes in a block or the mortar has given way. To prepare it for use (Lehner), we let milk stand in a cool place, skimming away with the utmost care all the cream. Place this on a filter, and pour on it rain-water till it is purified from every trace of lactic acid; then tie it in a cloth, boil it in water, and spread it on blotting-paper in a warm place, when it will be a horn-like substance. This will keep for a long time. To prepare it for use, rub it in a saucer with water.
To mend stone make the following:—
| Caseine | 12 |
| Slacked lime | 50 |
| Fine sand | 50 |
Another recipe:—
Boil new cheese in water till it draws out in threads, stirring in slacked lime and sifted wood-ashes in the following proportions:—
| Cheese | 100 |
| Water | 200 |
| Slacked lime | 25 |
| Wood-ashes | 20 |
This may also be used to close cavities in trees or in wood.