The penetrant test (PT) generally consists in the use of a red liquid with particular characteristics of viscosity and capillarity named “dye penetrant” and another white coloured called detector that allow the detection of defects opening on the surface of ferrous and non-ferrous materials. After applying the red liquid on the piece to be examined and having waited a few minutes for its penetration in discontinuities , it will be carefully removed from the surface, and the developer will be applied on the same giving evidence of flaws, recalling on the surface the part of dye penetrant that had not been previously removed by cleaning the piece ( because trapped in the discontinuity ) . Any defect will appear in red and will be visible to the eye and evaluated . It is possible, alternatively to this type of products, to use fluorescent liquids with a UV lamp to obtain a more reliable result.
