ASTM D5397 Clarification

Q: I need some clarification regarding ASTM D5397. One of our baths is having an issue with the agitator. Does it impact the testing if the solution is not agitated continuously?

A: Unfortunately, the agitator is a major factor affecting the results. IGEPAL® CO-630 is fragile over the long term and needs to be kept agitated at 50 degrees Celsius in the bath throughout the test exposure (i.e., 500-3,000 hours). If not, the surfactant segregates in water and becomes ineffective. Keeping a stable bath from both a temperature and mixing standpoint is often checked by the cloud point and pH of the solution. To further  complicate matters, IGEPAL CO-630 solution is corrosive and more viscous than water alone. You will need to buy a new robust pump/stirrer.