Is Water Washable The Same As Water Based?
Is Water Washable The Same As Water Based?
We recently had a customer call who was being pressed by an auditor to prove that the level 3 water washable penetrant he was using, (Met-L-Chek FP-923), was not a water-based penetrant. Being pressed by an auditor is nothing new to hear about but this question came out of left field. It brings up the comparison of water washable and water-based penetrants, and how to easily tell which is which.
The easiest way is to read either the label, the product data sheet, or the certification that came with the penetrant, and to compare the product designation with the designation listed on the QPL. A water based penetrant will be identified as such. The label and product data sheet will also have instructions concerning the concentration of water that is correct to insure that the sensitivity is maintained at the level specified by the QPL. These data may also be accompanied by a concentration chart. All of these items are only used for water based penetrants. In contrast, penetrants that are non-water based are used as they are supplied, and do not have any instructions on the label or product data sheet concerning the concentration required to meet the required sensitivity level.
But one could go further by reviewing the certificate of analysis of the penetrant, since water based penetrants and non water based penetrants have different acceptance tests. Non water based water washable penetrants must have a water content of less than 1%, and a water tolerance of at least 5%. Water based penetrants will obviously have a water content more than 1%, and their water tolerance is infinite.
But if all else fails, one can make a simple test. Take a bit of penetrant and add an equal amount of water. If the result is a clear liquid, it is a water based penetrant. If the result is cloudy or gel-like, it is not water based