Ask the Expert Question-and-Answer Archive

by Ron Joseph

March, 2006

Latex Paint Odor

Q. I used to work for an organization that was donated a lot of older latex and oil, interior and exterior, paint to use in mission work. By their understanding, in order to check and see if the paint was good or not, someone had to smell it. Sour smell, the paint was bad. Regular paint smell, the paint was good. I wanted to know if there was any other way to check if paint was good or bad. It would save a lot of nostrils and a lot of time.

A. I have never heard of the "nostril quality control test", but I can understand why old latex paint might smell. Some waterborne paints have the potential to suport bacterial growth, and as you probably know high bacterial concentrations in water smell rancid. Old waterborne paint does smell,; however I'm not sure that you can assume that the paint is bad. You would need to apply a small quantity of paint to your substrate and evaluate it's performance before you can make a judgement. In fact, you might ask your paint vendor if you can add a biocide to the paint rather than toss the valuable product to hazardous waste site.

Best wishes,

Ron Joseph