#1 Gray Dry Method Non-Fluorescent Particles#1 Gray provides strong contrast on most metal surfaces during dry method mag particle testing in visible light. It is ready to use for visible light flaw detection of surface and slightly subsurface discontinuities in ferrous metals. It can be used in a powder blower or shaken from a bottle during magnetization, and blown off while current is still being applied. On material with a high magnetic retentivity, indications can still be formed after the