A CEMENT which may be used in several combinations is made by dissolving fresh acidulated caseine (made by adding vinegar to milk, and carefully washing the deposit) in a very little caustic lye. It must be kept corked in bottles.
These caseine or cheese or curd cements hold well, but do not well resist water, except in powerful combination.
The excellence of cements depends to a great degree on the quality of the materials and the scrupulous observance of care in making. Thus for the following, for glass:—
| Glue | 200 |
| Water | 100 |
| Calcined lime | 50 |
in which we have one of the commonest and oldest formulas, the value depends on “the make-up” that is, the glue must be left in cold water for two days, then boiled in a balneum mariæ, or a double kettle, in lukewarm water; that is, it must not boil, or the glue will be weakened.
The so-called Diamond or Turkish Cement, for glass or any other fine work, has been known since early times as incredibly strong. Its formula, according to Lehner, is as follows:—
| I. | Sturgeon’s bladder | 20 |
| Water | 140 | |
| Spirits of wine | 60 | |
| II. | Gum-mastic | 10 |
| Alcohol | 80 | |
| III. | Gum-ammoniac | 6 |
These are three separate portions, No. I. being prepared by warming and filtering. The gum-ammoniac is reserved from the others, and added after they are mingled.
A strong base for a cement for glass, as well as wood or stone, is made by gradually stirring finely sifted wood-ashes into silicate of soda, or strong acid glue, till a syrup-like substance results. In America the best ashes for this purpose are those of the hickory. Perhaps beech wood yields them equally good.
There is a Diamond Cement which is of special value to attach gems to rings or metal, to make coral or pearl or ivory adhere together, and, in short, for all fine work where a very strong adhesive is required. It is as follows:—