Document LpZ0V0010Go4mmoM6YZpM7nyw

I? fit 00! Cl. Oc Graves, Wilia.:., P~?0l4 *#'H* Baadlas, mira,, 3MJ030 0* B. Bullitt, Wllia,, B-70I6 J* D* MeBura^f, Wlliiu, P-7012 Jo Do Pickens, Flint Bo B, Thomas, iewburgh Jo Wo Iliff, .Lab, Russell Morgan- Lab, 0. So Bo Merkle, into Po B, Evans, Lab. Paul Eobinson, Lmb All Marshall tab. fmpv. & Group Loaders Indexed Marshall Laboratory Marsh 24, 1952 s" * * fir 81 '52 MBHPBAMPDM REPOET WO. &.LLD MBASQBEMBST OF FILM THICK1BSS OP PAIKT FILMS S &&2sdass&^ J An accurate and convenient method of ssasurlng film tMck ness of paints while still adhered to the substrate is available in the- us of Zeis optioal slit microscope. This method la more accurate than the ordinary aieroieter method and just as easy to use. The method is applicable to film thickness measurements of paint film on any substrate, but is especially useful for paint on plate glass panels. Film thickness f the individual coats of a multiple cost system may he measured also, provided there is sufficient contrast between the colors of the coats to make them distinguishable by the human eye. 3&8tt8s&L The Zeiss optical slit microscope is designed for .measuring surface roughness,, ia, depth of scratches in the surface. Thus if a .small section f paint is removed from the substrate, the equivalent of a scratch is made la the paint film the depth of which is the thickness of the paint film. In the case of one coat systems the sides of the cut may be perpendicular to the surface of the substrate or at a slight angle. In the case of multiple coat systems in which the. individual coat thickness is desired the sides of the cut must be at approximately 45* to the surface of the substrata* A complete pt the .operation of the Zeis optical slit microscope may be found in TB51?~0, N35445 This method m& developed by measuring the depth of 10 scratches, the depth of which were knows (by micrometer) Each of these scratches was measured 3 times . and the average f the three taken as the depth of the .scratch The results of the measurements mad with the .optical slit microscope compared t the actual depths are shown in figure 1. These measurements were ma# using the 7* objective TABLE I 2,,40 3. 50 5 50 6 90 9.90 2 10 3* 30 6.70 9.90 540 44 69 110 137 190 41 68 132 198 10? 2.20 3.54 5 50 6.85 9*90 2.25 340 6.60 9*90 5.35 From fig. 1 the calibration is found t be 1 division *O0S ail,, The confidence limits of this method based on 3 measurements with the 71 objective is for a coat systems Clpt; v o 06 mil. The standard deviation based on 10 measurement is f .,02 .mil SPBicms 3/20/52-R 3/24/52-? miSHALL LABQEATGHf B. P. BRXOOTELL DUP030003371 of* on o9t o f t o-Hi o f t t r on 091 06 o& 04 o? o j *+ / j \ 'k