238 



The Philippine Journal of Science 



are not uniform; they become thicker in the center than at the 

 edges because of surface tension. 



2. The amalgam method consists in painting over a piece of 

 tin plate. 8 After the paint is dry, it is scratched at a few 

 points and drops of mercury are placed on the scratches. The 

 mercury amalgamates with the tin, and the paint film can be 

 lifted off the semiliquid amalgam. The quantity of tin and mer- 

 cury needed, the necessity for using only unrusted tin plate, and 

 the time required to remove the film from the tin militate against 

 the usefulness of this method. 







, 













Time 



in days. 



10 



12 13 I 









IS I 



















































N 

























LEGEND 

















\ 



















— — — — Lmieed oil boiled. 



iumbang boto oil, 6 months old. 



Lumbang banucolog oil, boiled. 



— ■■■"■■ Linseed oil fresh. 



—iumbang bato oil, fresh. 



iumbona banucolog oil, fresh. 













V' 







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Fio. 1. Comparative drying tests for linseed, lumbang bato, and lumbang banucalag oils. 



3. Lipowitz or Wood's metal can be also used. The metal is 

 coated with the paint under examination. After the paint is 

 dry, the metal is put on a smooth plate and gently warmed. At 

 a temperature below its melting point (60° C.) the metal softens 

 sufficiently to allow the stripping of the paint. Satisfactory 

 paint films can be made in this way. This process is not well 

 adapted to laboratory work because of the large amount of ex- 

 pensive alloy required and the care necessary in removing a film. 



' Emsmann, D. H., in Brannt, W. T., Varnishes, Lacquers, Printing Inks 

 and Sealing Waxes. H. C. Baird Co., Phila. (1893), 321. 



