PHYSICAL LABORATORY PAINT TESTS 



87 



table is a convenient accessory of the microscope, and its use is 

 to be recommended. A glass slide being placed in position upon 

 the turn-table, a very small amount of either the pigment rubbed 

 up in oil, or the paint, is applied to the slide; a small drop of 

 Canada balsam is then applied by means of a glass rod dipped 

 in a solution of balsam in xylol, and dropped upon the slide. 

 The rod is then used to thoroughly incorporate the pigment with 

 the balsam, and a cleaned cover glass is dropped over the whole 

 and pressed down tightly, so that a small amount of balsam will 

 exude from under the edges and thus firmly seal the glass. In 

 order to make permanent slides it has been found advisable to 

 rim the cover glass with balsam and even follow this up with 

 some suitable black varnish, the slide being then carefully labeled 

 and placed in the collection. Following is a table of the charac- 

 teristics of the fourteen chief pigments : 



TABLE OF THE SIZE OF PARTICLES OF THE CHIEF PIGMENTS WITH THEIR 

 CHARACTERISTICS UNDER THE MICROSCOPE 



Film Sectioning and Deductions to be Drawn Therefrom. 5. 



Investigations were undertaken into the innermost structure 

 of paint films as revealed under the microscope. Up to the 

 present time, work has been done upon barytes, asbestine, blanc 

 fixe, and white lead, painted upon wood, and a combination 

 paint upon wood. The films, the preparation of which has 

 been described in the foregoing, were sectioned and prepared 

 for microscopic examination in the following manner: 



