DPT is low cost method of detecting surface breaking flaws, such as cracks, cold laps, porosity etc. Dye penetrant is drawn into a surface breaking flaw by capillary action and excess surface penetrant is then removed; a developer is then applied to the surface, drawing out the penetrant in the crack and producing a surface indication. The technique can be applied to many non-porous clean materials, metallic or non-metallic.