Materials Engineering, Evaluation, and Inspection

Liquid Dye Penetrant Testing

Spectrum uses Liquid Dye Penetrant Testing to detect discontinuities that are open to the surface in both ferrous and nonferrous test materials. Liquid penetrant testing can distinguish surface discontinuities such as cracks, seams, laps, cold shuts, laminations and porosity. Red dyes visible in ordinary light, as well as fluorescent dyes visible under ultraviolet light, are used in our processes, along with a developer. The developer is a thin powder coating, normally applied by an aerosol, which draws the penetrant out of any discontinuities while providing a contrasting background to increase the discernibility of discontinuities. Typical candidates for Liquid Dye Penetrant Testing include welds and weld overlays, castings, forgings, valves, machined parts, pressure vessels, vessel linings and structural steel. It is often used on non-ferromagnetic materials for which techniques such as magnetic particle inspection are not appropriate.


  • Used on nonporous materials
  • Can be applied to welds, tubing, brazing, castings, billets, forgings, aluminum parts, turbine blades and disks, gears


  • Need access to test surface Defects must be surface breaking Decontamination & pre-cleaning of test
  • surface may be needed
  • Vapor hazard
  • Very tight and shallow defects difficult to find
  • Depth of flaw not indicated
  • Best results are achieved within a temperature range of 4C to 52C