J. M. Ordway on Waterglass. 345 
Silicate paint, being itself unyielding, is much more suitable 
for unyielding surfaces, as for glass, stone, or brick, or for walls 
plastered with lime mortar. As it unites more intimately with 
such substances, it is less liable to scale off from them than from 
wood. But to guard against a loose adhesion, it is better in all 
Cases, to paint with a very thin waterglass several times, allow- 
ing some days to elapse between the successive applications, 
rather than to use a strong solution once. The thinner silicate 
penetrates deeper and takes a surer hold. It is also sooner and 
more uniformly fixed by the absorption of carbonic acid. 
Many pigments are incompatible with waterglass, and must be 
rejected. Such are white lead, Prussian blue, Schweinfurth 
green, and animal or vegetable colors. But there is still left a 
sufficient variety to select from, as we may take zinc white,* chalk, 
sulphate of baryta, yellow ochre, cadmium yellow, Venetian red, 
terra di Sienna, green oxyd of chrome, umber, ultramarine, 
lampblack, or bone black. It is said that chrome yellow and 
ome red may also be used, but it would be safer to leave 
them out, as their chemical relations indicate their unsuitableness. 
: fore applying colors ground up with waterglass, it is best to 
prime’ the surface with simple silicate liquor, and let it stand 
not exceed the sp. gr. 
Weaker, Much of the silicate of soda found in the market in 
this country, is unfit for paint. It is sometimes too alkaline, and 
18 very often too much contaminated with foreign salts which 
are prone to crystallize and loosen the silica before it becomes 
Saeed fixed. A good silicate should be bright, transparent, 
omogeneous, and very light colored, and should show no special 
tendency to absorb moisture in a damp atmosphere. It is none 
the Worse for requiring several hours boiling to bring it into 
Solution, provided this refractoriness does not arise from y 
matter in combination. 
Walls plastered with lime mortar, may be rendered very hard, 
close and smooth, as well as capable of being washed, by apply: 
ing a few times a silicate, either alone, or mixed with chalk or 
we: coloring material. 
ince 1840 Fuchs has introduced a new plan of executing 
Works of art on plastered walls, designating his method by the 
name of “stereochrome,”—/ast paint. A basis 1s es a 
with a rather sandy lime mortar, and when this has taken up a 
due proportion of carbonic acid and become well set, the super- 
nm “ ine white sets rapidly with 
wikieet ra * = standard works it an ae te yee rt pin y vata 
Without any change, 
Jour, Sci.—Srconp Szxtms, Vou. XXXII, No. 96.—Nov., 1861. 
44 
