72 PAINT TECHNOLOGY AND TESTS 



carefully prepared and numbered and given three coats of a white 

 paint formula of the corresponding number. After drying, the 

 boards were carefully weighed and immersed in a tub of water 

 for three weeks. After removal, the surfaces of the boards were 

 dried with blotting paper and the boards weighed. The gain 

 in weight, corresponding to the amount of water penetrating 

 through the pores of the wood, was observed. The boards were 

 again immersed and at the end of two months the following 

 results were obtained: 



Grammes of water 



Formula absorbed 



No. through paint 



1. Soya bean oil 120 



2. Linseed oil 102 



3. Calcium sulphate 93 



4. Barytes 88 



5. Asbestine 74 



6. Corroded white lead 59 



Basic carb. White lead 25% 

 Basic sulph. White lead 20% 



7. Zinc oxide 25% 58 



Calcium sulphate 25% 



Calcium carbonate 5% . 



8. Sublimed white lead 56 



9. Zinc oxide 56 



( Zinc lead white 30% ] 



, n ! Zinc oxide 40% ! 49 



iu> 1 Basic carb. White lead 20% I 



{ Calcium carbonate 10% J 



, . ( Basic carb. White lead 50% 

 u< \ Zinc oxide 50% 



f Basic carb. White lead 38% 

 12. \ Zinc oxide 48% 38 



[ Silica 14% J 



The test boards were then exposed, with their content of 

 water, to the action of the sun's rays. Blistering of the painted 

 surfaces took place in many cases, caused by the rapid with- 

 drawal of the water and its consequent action on the paint film. 

 The tests seem to indicate that a mixture of white lead and zinc 

 oxide, with or without a small percentage of the inert pigments, 

 is not as subject to the action of the water as the single pigment 

 paints. In order, however, to corroborate these tests, it occurred 

 to the writer to develop a more visible means of demonstrating 

 the passage of moisture through paint films. 



Another series of white pine boards were therefore soaked in 

 a solution of iron sulphate for several hours. After removal, the 

 surface of each board was dried and coated with one coat of the 



