A very strong, clean cement for porcelain or glass is made as follows:—
| Well-cleaned | glass powder | 10 |
| ” | fluor spar powder | 20 |
| Silicate of soda solution | 60 | |
This must be very quickly stirred and applied. This is one of the hardest and best cements, and it resists heat and other influences so well that when very carefully amalgamated it may be applied to the manufacture of many useful articles. The same may be made with the substitution of white pipeclay for fluor spar, or with the addition of the same in somewhat larger proportion. Pipeclay or any good clay can also be combined with glycerine to prevent its drying. With gelatine and a little glycerine it will harden and not crack.
This requires careful amalgamation and rapid work.
To prepare very fine glass-powder for this cement, heat any glass till red-hot, then drop it into cold water. It may then be reduced in a mortar to an impalpable powder.
Earthenware tubes or pipes which are to be exposed to intense heat may be luted or joined with the following cement:—
| Peroxide of manganese | 80 |
| White oxide of zinc | 100 |
| Silicate of soda | 20 |
“This does not melt, save at a very high temperature; and when melted it forms a glassy substance, which holds with extreme tenacity” (Lehner).
To prepare caseine cement for crockery or marble, it may be observed that we should always take fresh white cheese and macerate or knead it thoroughly till only pure CASEINE adding to this one-third of powdered quicklime and blending the two ingredients very thoroughly we get a very strong glue. An admixture of 10 parts silicate of soda also forms a powerful cement.