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1950-51 Theatre Catalog, 9th Edition, Page 425 (403)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 425
Page 425

1950-51 Theatre Catalog, 9th Edition, Page 425

comes slightly transluscent or darker and appears somewhat less satisfactory than when dry; but, on drying out, the film returns to its original color and opaqueness. Tinted paint films also assume a deeper color when wetted.

Durability depends on several factors, including the composition of the paint, texture and cleanness of the concrete surface, application procedure, and severity of the exposure. It appears that Portland cement paints, properly applied to exterior wall surfaces exposed to the weather, may be expected to have a surface life of about eight years. Some cement paint jobs last considerably longer, some are IeSS durable. The less durable jobs frequently are those involving smooth, dense concrete surfaces where there is a tendency to brush out the paint too thin and to neglect the requirements for satisfactory adhesion.

Effiorescence-Generally it is advisable to defer painting of new masonry until efiiorescence has become negligible. In the case of tinted cement water paints for use on cast-in-place concrete walls, several months should be allowed for the concrete to cure before painting, to lessen the liklihood of efflorescence.

To remove emorescence, first wet the concrete, then apply a 20 percent solution of muriatic acid and, after about five minutes, scour off the efflorescence with stiff bristle brushes. If necessary, a stronger solution may be used. The surface must then be thoroughly washed with clean water to remove all traces of acid.

Any traces of oil must also be removed from the surface.

Before applying the paint, the concrete should be thoroughly wetted to control surface suction and to provide a reserve of moisture to aid in the proper hardening of the paint. A garden hose adjusted to give a fine spray is well suited for this purpose. A superficial dampening with a brush dipped in a bucket of water, as it often done, is wholly inadequate.

Usually it is sumcient to wet concrete masonry walls or other concrete that readily absorbs moisture in one operation not more than 1 hour before painting. The spray should be applied in such a manner that each part is sprayed three or four times for about 5 to 10 seconds, depending upon the absorptivity of the surface, the time being allowed between is for the moisture to soak into the concrete; the unabsorbed water serves no purpose. If the surface tends to dry rapidly, as it may in hot weather, it should be redampened slightly just in advance of painting; it should be moist but not dripping wet or with a noticeable water film when the paint is applied.

Dense concrete absorbs moisture so slowly that it should be wetted in at least two operations not less than 30 minutes apart. It will be more effective to dampen rather large areas in advance of painting so that ample time is allowed for the moisture to soak into the concrete. When the paint is applied, the concrete surface should be moist, but without free water; some suction is necessary.

Preparation of Paintwllortland cement paints are made ready for use by thoroughly mixing the paint powder and aggregate, if used, with water in the proper proportions.


A PORT'LAND'CEMENT BA-SE PAINT, properly applied and cured. will give many years of service. These eight pictures, prowded by W. D. M. Allen and the Portland Cement Association, show the method of application. Top picture shows the measuring of the dry paint powder and the water according to directions. Then (bottom picture) thoroughly mix to the consistency of thick cream.
1950-51 Theatre Catalog, 9th Edition, Page 425