PHYSICAL LABORATORY PAINT TESTS 71 



We now come to a method worked out in our laboratories, which 

 can be recommended as being not only simple but efficient and 

 practical. It has been found that a size from noodle glue, when 

 painted upon ordinary fair-quality paper, makes a surface from 

 which the paint may be subsequently stripped. The paint is 

 applied in the ordinary way to the paper, which is held during 

 the operation by thumb tacks, and allowed to dry. The paint 

 may be separated by immersion in water kept at about 50 degrees 

 Centigrade. By this method large films may be obtained, but it 

 has been found very unhandy to work with films exceeding an 



Bottles Showing Relative Permeability of Films by Amount of Whit- 

 ing Formed Within 



area of eight inches square. When the film of paint has been 

 detached from the sized paper through the dissolving of the 

 noodle glue, the paint film is then immersed in a fresh solution 

 of water, in order to remove whatever excess of noodle glue there 

 may be remaining. A glass rod is then introduced into the 

 bath, in which the paint film is floated upon the glass rod, which 

 is then hung up to dry in a suitable container to prevent the 

 accumulation of dust, etc. 



The Permeability of Paint Films. A series of tests were made 

 to determine the water-excluding values of various combinations 

 of painting pigments ground in pure linseed oil. White pine 

 boards, six inches long, four inches wide, and one inch thick, were 



