128 PAINT TECHNOLOGY AND TESTS 



paint being chalked to a great extent and showing rapid de- 

 composition of the binder or vehicle. Inasmuch as lithopone 

 is really an inert pigment, this rapid decomposition of its 

 vehicle cannot be explained in the same way as the decompo- 

 sition of the vehicle of pure white lead paints, where the alka- 

 line nature of the lead is probably responsible for the formation 

 of easily destroyed compounds. As complete failure had taken 

 place in nearly every case where lithopone had been used, it was 

 decided to condemn the lithopone panels on the fence, consist- 

 ing of formulas 21 to 27, including panels 151 to 164 in white, 

 panels 131 to 144 in yellow, and 109 to 122 in gray. These 

 lithopone tests were later on replaced by new tests in 1909, 

 which will be reported upon later in this book. 



General Results. From these tests, the inspectors reached 

 the unanimous conclusion that a paint made from any mixture 

 of more than one white opaque pigment, either when used alone 

 or in combination with small percentages of inert pigments, 

 is far superior to any one single pigment paint. It was found 

 that the straight white lead paints failed in every case, and this 

 failure was so marked as to make it a conclusive demonstration 

 of the unfitness of white lead along the Atlantic coast, when 

 used without other pigments. Paints made with large percen- 

 tages of white lead, however, gave excellent results. 



Gypsum was found unsafe to use in any large proportion in 

 a paint, because of its solubility and liability to percolate through 

 the coating of linoxyn or dried film, thus destroying the surface 

 of the paint. Whiting, or calcium carbonate, demonstrated 

 that it could be used in moderate percentage with some efficiency, 

 but it was evident that any great excess of this pigment must also 

 be avoided on account of its tendency towards rapid chalking. 

 Magnesium silicate, aluminum silicate, and silica are three 

 inert pigments which proved to be of great value in strengthen- 

 ing and reinforcing paints, especially when they were- used in 

 small percentage. In the same way, black fixe and barytes, or 

 barium sulphate, also appeared to be useful in strengthening a 

 paint. As these two last named pigments are chemically the 

 same but physically different, the use of both in a paint formula 

 is considered advantageous, because of the differences in size 

 and form of their particles. 



Color Tests. It was the unanimous conclusion of all the 



