in contrast to this desire for widespread penetrant testing, how-ever there is the general fear that components or welds tested with the dye penetrant and which are used in the environment of cryo-vacuum and particularly in the ultra-high vacuum conditions are contaminated by the dye in such a way that they do not ful-fill the cleanliness requirements for vacuum components. this fear is mainly based on the high penetrant property of the dye and its particular creeping characteristics, which just is the property required for test procedure.