the Helling's Nordtest series was used as PT testing medium. This series consists of the penetrant U89,cleaner U87 and developer U89. The detailed composition of the medium was not available from the company. Only the information of the material safety data sheets (3) is available. According to this the penetrant consists of fatty acid ester (hydrocarbon) and the diazo dye Solvent Red 164 (a compound of hydrocarbon and nitrohen). The cleaner medium consists of ethanol. Cleaner and developer are in an aerosol (injecting fluid: propane and butane). Only the penetrant is criti-cal for the contamination pars because of its high penetrating property (Fig. 2).