Hello,

please tell, which is the minumum depht
(in microns) of a discontinuaty in steel to be detected by dye penetrant testing?

I see (without a magnifying glassa) a crack (length is 5 mm) on perfectly cleaned tested surface, but using of dye penetrant testing does not give an indication. I understand, that it is a surface crack and want to know what is the minimum depht of a discontinuaty to be detected by dye penetrant testing.