Document 998d7Kg7w9mKK0q5LQ8Q507v6

oc P, B Evans,. E&b, ' Stuart Graves, Lab, Piles 7.838 111 7260 0886 ^S^.'tSS^INppED" &7;r%% mummxto r e p c k t h o . &-4S3 , ., ,. .. _ M COPf -*mt . ?i c e c p MOISTURE BLlSTERim OP MM & SHUTTER WHITE OVER ' PBEVXOPSLY PAIHTED SURFACE Sine .Research Report lo, 1069 was written, two additional studies.hav compared alkyd whit and #40 $M.t over previously painted wood on the moisture test house*. In Series 1238X-.there`are three comparisons,...The films, were aged two months In ' Florida, Rad blistering occurred: with all systemso There is -an average difference of =>0,2 blister rating units'with & 70$ probability of chance, This confirms Series 9936 cited in the research report where'no significant- difference was., found between T* & S, White and #40 Whit m previously painted : panels, .' In "Series 11538, duplicate'Comparisons have been mad ,. for each pf two periods of weathering. This study chows a station tieally significant 'difference in favor of the control,, For the 1950 tost, both blistered but T, & 3, .Whit. was 1,6 + 1,1 units worse oh the average# la the 1951 test, the control did not blister, and To & S, White was 1,1 units worse on the .average, This study conflicts with Series 9938 and 12561, Obs@r nations on the film integrity of the control .explain partly.or wholly why the house paint blistered less in this study. The film had broken down by cracking after on year of exposure, in Florida, The Cracking took place on. new wood a well as over previous paint, Ch the previously painted panels the paint film split longitudinally down to the wood,- .Although the panels were, rated'perfect in regard to: blistering',...they actually had failed by a,different process, '"".'The rapid'Breakdown'of the house paint control in this series might be caused * (1) by .a flute in making the. paint in the ' laboratoryj .(2)' by application of very, thin film, The panel were not prepared by the panel exposure .group, m& they was' .no' control of spreading rat, MARSHALL LABORATORY `VM* WPStai-, 4/24/5 WXLtftU'T F* SXM&lSTOf