The detection of the surface cracks and flaws by the use of the dyes. These may be flourescent or colored. The dye contains wetting agents to make them flow evenly into very fine cracks. Depending on the type of defect sought, the dye is left to penetrate for a period of from 5 to 10 minutes. Surface dye is by then removed and a developer applied. Where there is crack, dye is drawn out by the developer leaving an easily visible indication above the crack.
To detect severity of open to the surface discontinuities on welds of:
- Magnifying glass
- Flash light
- Welding pit gauge
- Inspection mirror