Methods Used at Inspection. One of the most important tests made when inspecting paint is the determination of the chalking taking place.[16] There was developed during the inspection of the Atlantic City panels a new method for determining the comparative chalking of the various paints. It was thought desirable to secure a method, if possible, that would show results which might be photographed and even tabulated in percentage form, if desired. The apparatus for the new test consisted of a small strip of black felt three inches wide by five inches long, placed across a small block of wood which would fit in the palm of the inspector’s hand. This outfit resembled a blackboard eraser and was used in a similar way. By holding the apparatus firmly against the panel and drawing it half-way across the panel in a straight line toward the operator, there was obtained on the black cloth a white mark proportional in intensity to the amount of chalking which had taken place on the given area. When a series of these cloths were made, they were assembled and photographed for comparison. It should be noted that the above chalking test is useful only where the painted panels under examination have been exposed over a period of one to two years, during which period the chalking of paints has been shown to be greatest and the chalked surface of a fairly adherent nature. Where longer exposures have been made and where rains have removed from the painted panels a considerable amount of the chalked pigment which has formed, such a test would not be fairly representative of the amount of chalking which had taken place.
[16] Mr. Macgregor of the Picher Lead Co. has just developed a new test to determine the relative imperviousness of paints which have begun to chalk. He draws a mark about two inches long upon the painted surface with a fountain pen. The ink mark will spread rapidly to a wide area if the chalking is of a bad order. If the chalking is slight and the film in good condition, the ink mark will not spread.
Series of Black Felt Cloths used in making the Chalk Tests on the Various Formulas. Numbers over Cloths represent Panels
CHALKING.—Type of Decay Exhibited by Improperly Made Paint (magnified view)
