Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/129

Rh It is important to notice that in all cases of practically testing paints the results are obtained by comparisons being made, and hence it is necessary in every case to have a standard with which to compare the sample to be tested as has already been explained.

The test of painting over squares of black and white may be varied by using stripes instead. The test answers equally well for white lead, zinc or any color of which the quality of body is of importance. In some colors it is of little moment.

Tinting or Staining Strength. Any painter can test the tinting strength of any color himself in a very simple manner. All that is necessary is to have a pair of druggists' scales, some blotting paper, a palette knife, some pieces of glass or a flat piece of marble and some pieces of waxed paper. First weigh out say eighty grains of dry white lead or dry zinc. Any other white will answer equally well. Place these eighty grains on one side of the glass and the second eighty grains on the other. Now take the dry color and weigh one grain and add that to one of the little piles of white, then weigh a grain of the standard color and add that to the other pile. Now add to each pile a few drops of oil, taking care that the number of drops is the same in each case. With the palette knife thoroughly mix until no streaks can be seen and the mixture is perfectly uniform. Then by comparing the two the difference in tinting strength will at once be apparent. The same result would have been produced had ordinary white lead ground in oil been used instead of dry lead or zinc. If the color is ground in oil a little difference in the method must be observed, the reason being that one color might be ground much thinner than the other, in other words might contain much more oil than the other, and hence if equal weights of each were compared the result would be misleading. Take then each color in oil, that is the standard and the color with which it is to be compared,