Document EdQgz99NV8ay9VE7k2jLXO6m0

Cross Index: 7it a ; (Punched card system) kit CCsMJ. D. Pickens,Flint P. B. Evans, Laboratory H, Lowell, " S, 0, Homing , " Kill NW R| CO MEMORANDUM REPORT MO. M-33' Marshall Laboratory January.22, 1951 GLOSS MEASUREMEKTS IH EXPOSURE STUDIES k) In the course of our study on film deterioration we havs^ utilized gloss measurements as a means of following degradation. From data for our control series using 9fy~p6o67S we have determined on the basis of many replicates that utilizing our procedure the average standard; deviation is only 2 gloss units. We have followed loss of both 60 gloss and 20 gloss as measured with the duPont'Universal Glossmeter. \ It ..has been determined that the first signs of film failure \ are conversion of an originally hydrophobic surface to an hydro* ph.il.lic one and a nearly simultaneous development of a surface ` disruption which is not apparent to the eye, but which can be followed \ reproducibly by 20 gloss measurements. This is stem in the attached ^ graph. It is entirely possible that loss of 20 gloss to a prede termined low value or 0 will be reproducible and directly related to the ultimate durability of a finish. If this should prove to be the case, it would mean that durability results could be obtained in 3 or k months for most finishes, (94-p~6o678 as prepared for this series seems to have outstanding durability), It is suggested that this method be tridd in cases where early results are desired, and interested parties could investigate its applicability by the simple experiment of putting out 6 panels to be returned in duplicate after 3, 4 and 5 months exposure (or 9 panels if triplicate data is preferred), and correlating results with the "ultimate" durability. A control should of course be used since outdoor exposure is variable. In uitlizlng this method we have measured the initial gloss, and on receipt of the panels from Florida washed them very carefully with a soft cloth using a Dupinol solution* The panels were then rinsed, blotted dry and gloss measurements made on the clean panels. JRK:ms ATTACH: MARSHALL LABQRATORT --" J/ R/H^fTSBERC EXPOSURE VS GLOSS FOR 94 P-60678 BOOTHS EXPOSURE IN FLORIDA