218 PAINT TECHNOLOGY AND TESTS 



Test No. 8. Concrete primed with one coat of white paint 

 of the following composition: 



PRIMER 



Zinc oxide 25% 



Silica : 35% 



Corroded white lead 20% 



Gypsum , 15% 



Whiting, etc 5% 



Ground in a vehicle of linseed oil and containing 35% of volatile hydro- 

 carbon spirits and drier. 



This coat was followed by one of the following composition, 

 tinted blue: 



Zinc oxide 60% 



Gypsum 20% 



Silica 20% 



Ground in linseed oil with 12% of turpentine and drier. 



Fair results shown during first year, but a breakdown occurred 

 during the second year, and cracking and scaling resulted. 



Test. No. 9. This test was a duplicate of No. 8 with the 

 addition of 5% of zinc sulphate solution emulsified into the 

 primer. 



Slightly superior to Test No. 8. 



Test No. 10. Primed with a white paste paint thinned with 

 turpentine. Second coated with same paint tinted blue. 



FORMULA OF PASTE 



Zinc oxide 40% 



Whiting 30% 



Silica 20% 



Alumina and gypsum 10% 



Ground in 16% of linseed oil vehicle. 



Scaling and peeling due to lack of binder and use of sapon- 

 ifiable oil resulted during the first six months' exposure. Entire 

 destruction of coating at end of two years. 



Test No. ii. Primed with a white mixture, and second coated 

 with the same mixture tinted blue. 



FORMULA OF MIXTURE 



Whiting 30% 



Silica 30% 



Zinc oxide 40% 



Stirred into a 5% solution of glue in water, until a fairly thick paste was 

 obtained. 



