CEMENT AND CONCRETE PAINT TESTS 215 



Acid Reacting Compounds. A series of acid reacting washes 

 were included in the tests, having been designed as prime coaters 

 for use previous to the application of oil paints. The application 

 of many of these washes has the effect of neutralizing the lime 

 within cement and concrete surfaces, and often precipitate in- 

 soluble lime compounds which aid in filling up the outer voids, 

 thus presenting a surface more suitable to receive oil coatings. 

 To the writer who has since made a careful study of the painting 

 of concrete, it would seem advisable for painters to avoid, when 

 possible, the use of these lime neutralizing washes, as some of 

 them have more or less disintegrating and weakening influences 



View of Concrete Paint Test Panels 



upon concrete. Recent laboratory experiments, however, have 

 indicated that zinc sulphate, an acid reacting material used for 

 many years as a wash for concrete surfaces by Macnichol, actually 

 has a strengthening effect upon cement and concrete surfaces. 

 The more successful coatings of to-day, however, are those which 

 may be placed directly upon the cement and concrete surfaces 

 without the aid of such washes. Several fairly successful paints 

 of this type have recently appeared in the market; some of them 

 being made of acid rosins compounded with vegetable oils. 

 Probably one of the first mixtures of this sort was the so-called 

 suction varnish which the master painter has for years used as 

 a prime coating on plastered walls previous to painting. These 

 suction varnishes generally contain a high percentage of rosin, 



