How much contamination can WW penetrants tolerate with no sign of gelling or separation?

• A. 1%
• B. 3%
• C. 7%
• D. 5%

Answer: (D)

Water-washable penetrants must stay uniform and liquid even if there’s a small amount of contamination. The standard tolerance is five percent because at or below this level the penetrant remains flowable enough to enter surface defects and still be effectively washed off later without components separating or the mix gelling.

If contamination goes above five percent, the mixture can gel or separate, breaking the balance of the penetrant system. That instability leads to poor wetting, reduced penetration into cracks or porosities, and unreliable indications after developing and rinsing. So five percent is the practical, accepted limit to maintain reliable performance.

The other values would either be too strict for typical field conditions (causing unnecessary waste) or too lenient (risking gelation and separation that undermine detection).