Authorities are divided upon the successful results of the preservation of stone by silicates. Some claim in the affirmative that the protection is permanent, while others assert that with time and the humidity of the atmosphere the beneficial effects gradually disappear. It might be worth while to experiment upon some of the porous sandstones, which, under the extreme influence of our climate, rapidly deteriorate; such, for instance, as the Connecticut sandstone, so popular at one time as a building material, but which is now generally discarded, owing to its tendency to crumble to pieces when exposed to the weather even for a few years.
Soluble glass has also been used in Germany to a great extent for mural painting, known as stereochromy. The process consists in first laying a ground with a lime water; when this is thoroughly dry, it is soaked with a solution of silicate of soda. When this has completely solidified, the upper coating is applied to the thickness of about one-sixteenth of an inch, and should be put on very evenly. It is then rubbed with fine sandstone to roughen the surface. When thoroughly dry, the colors are applied with water; the wall is also frequently sprinkled with water. The colors are now set by using a mixture of silicate of potash completely saturated with silica, with a basic silicate of soda (a flint liquor with soda base, obtained by melting 2 parts sand with 3 parts of carbonate of soda). As the colors applied do not stand the action of the brush, the soluble glass is projected against the wall by means of a spray. After a few days the walls should be washed with alcohol to remove the dust and alkali liberated.
The colors used for this style of painting are zinc white, green oxide of chrome, cobalt green, chromate of lead, colcothar, ochers, and ultramarine.
Soluble glass has also been used in the manufacture of soaps made with palm and cocoanut oil; this body renders them more alkaline and harder.
Interesting experiments have been made with soluble glass for coloring corals and shells. By plunging silicated shells into hot solutions of salts of chrome, nickel, cobalt, or copper, beautiful dyes in yellow, green, and blue are produced. Here seems to be a field for further application of this discovery.