This standard defines a method of penetrant testing used to detect discontinuities, e.g. cracks, laps, folds, porosity and lack of fusion, which are open to the surface of the material to be tested. It is mainly applied to metallic materials, but can also be performed on other materials, provided that they are inert to the test media and they are not excessively porous, examples of which are castings, forgings, welds, ceramics, etc. This standard is not intended to be used for acceptance criteria and gives no information relating to the suitability of individual test systems for specific applications nor requirements for test equipment. The term `discontinuity' is used here in the sense that no evaluation concerning acceptability or non-acceptability is included. Methods for determining and monitoring the essential properties of penetrant testing products to be used are specified in ISO 3452-2 and ISO 3452-3.