Water Pre-rinse
ASTM E-1417 states (Paragraph 7.3.4.2) that “Hydrophilic post emulsifiable penetrant shall be removed with a water Pre-rinse, application of the hydrophilic emulsifier and then a post-rinse.” There is an unanswered question as to whether this applies equally to both immersion in the emulsifier and to emulsifier that is sprayed on. The answer may be found in the ASNT Penetrant Handbook, where it points out that the water Pre-rinse is for the purpose of limiting the amount of penetrant that is washed from the part into the emulsifier, thus extending the useful life of the emulsifier bath. When the emulsifier is sprayed onto the part, it is not reused, and so there is no equivalent rationale for using a Pre-rinse.