===+===================+======================+======================= | | Diameter in | Diameter in | | Millimeters | Inches | +-------+-------+------+-------+------+-------- No.|Name | Small | Aver. |Large | Small | Aver.| Large ---+-------------------+-------+-------+------+-------+------+-------- 1|Asbestine |.002 | -- |.12 |.00015 | -- |.049 2|China clay |.003 | -- |.065 |.00009 | -- |.025 3|Barium carbonate |.00076 |.0055 |.0172 |.00003 |.00024|.0011 4|Blanc fixe |.00073 |.0037 |.0073 |.00003 |.00014|.0003 5|Silex |.0037 |.0092 |.03 |.00014 |.00036|.0012 6|Gypsum |.0037 |.011 |.05 |.00014 |.00044|.0022 7|Amer.-Paris white |.0015 |.0050 |.04 |.00006 |.00022|.0018 8|Barytes |.0015 |.0092 |.05 |.00006 |.00036|.0021 9|Zinc lead |.00037 |.0018 |.0037 |.000014|.00007|.00014 10|Sublimed white lead|.00037 |.0018 |.0037 |.000014|.00007|.00014 11|Lithopone |.00076 |.0018 | -- |.00003 |.00007| -- 12|Zinc oxide |.00046 |.0018 |.00037|.00002 |.00007|.00014 13|Quick Pro. lead |.00061 |.0030 |.0048 |.00002 |.00012|.00018 14|Dutch Pro. lead |.00061 |.0018 |.0066 |.00002 |.00007|.00026 ===+===================+=======+=======+======+=======+======+======== =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: A solidifying dish was partly filled with low melting-point paraffin which was allowed to harden, when a small piece of paint was thrown upon it and then more paraffin poured over it. After hardening, sections were obtained of the paint film by means of a microtome. [Illustration: Section Barytes Film] A view of these sections of paint films under the microscope gave to the operator a better idea of the structure of a paint than had ever been afforded heretofore. It was easy to perceive the relative position of the pigment particles and the three coats. The penetration of one coat into another was easily discernible, and measurements were made upon the sections in order to determine the average thickness of coat and its general appearance. Sections were also made of Inside and Outside White upon wood. These sections revealed under the microscope the thickness of the coats and also the penetration of the priming coat into the wood. Appended is a table giving microscopic measurements. PAINT SECTION MEASUREMENTS UNDER MICROSCOPE