Dye penetrant testing

The dye penetrant method is one of the oldest non-destructive testing methods for detecting surface defects.
The test can be performed on almost all metallic and non-metallic materials.
In this method, the test liquid penetrates surface defects of any type of material due to capillary action. After carefully washing off the solution, a developer layer is applied to create counter-capillarity. This draws out the liquid that has penetrated into cavities and cracks and makes the defect visible.