Liquid Penetrant Testing is a very versatile method used to detect surface discontinuities in a wide variety of product forms. It is relatively cost effective and very portable in application. Although surface preparation is sometimes required, when using the visible method no electricity is needed. This makes it a very useful tool especially in remote field applications.
A bright red dye is applied to the surface of the test piece followed by a white contrasting developer to blot out dye that is trapped in a discontinuity. Indications are easily apparent and then characterized. Penetrant Testing can also be performed using the Fluorescent method. The procedure is basically the same as the visible but requires the use of an Ultraviolet light to enhance indications which are easily detected. The Fluorescent Penetrant method is considered to be more sensitive to very small shallow discontinuities.