How To Tell if Paint is Latex or Oil?

[John Ross]

This is a half bath in a home built in 1960. I want to repaint the walls and vanity cabinets.

Looking at the walls, it looks like it could be the original paint! It's not peeling, but has an appearance of being "thin"--it just doesn't look like the other bathroom where multiple layers of paint had been done over the years.

First question: If by chance it is the original paint, does that mean in must be oil (1960)?

Anyway, I want to put on a latex paint and I asked at a few paint stores and was told that if it is oil paint then I MUST use a OIL primer over the whole thing before the latex. Not something I want to do if not necessary.

I had heard that if you take denatured alcohol on latex paint it will come off, but on oil it won't do anything. I only have rubbing alcohol, so I tried that on a cotton swab and sure enough it took the paint off the wall. The cabinets are more confusing because the backs of the doors are a different color (original?) but when I rubbed the alcohol it took the color off (i.e. white streaks where alcohol rubbed). Plus, the inside of the main cabinet was painted and I doubt anyone every repainted that. Again, in there the alcohol made white marks, taking the color off.

Second question: Was using rubbing alcohol instead of denatured alcohol acceptable or by chance does it just take anything off and it was a meaningless test?

Any thoughts on what kind of paint is there or have I not done the correct test yet? If not is there other ways to determine?

Thanks in advance! John

[HeyBub]

1. Cover the existing paint with a primer and it doesn't really matter.
2. "Denatured" usually means some sort of posion has been added to an otherwise drinkable alcohol (i.e. Ethyl alcohol). Rubbing alcohol is Isopropyl alcohol. They're not the same, although chemically there isn't much difference.

[Roger Shoaf]

Rubbing alcohol works fine for the test, sounds to me like you have latex paint. Latex was used in the 60's.

[Deke]

Professionals can look and tell. For the rest of us, use the smell and taste test. If you have known paint samples, then the old smell and taste test will work every time. Use sandpaper to take off the top film and then smell of the item and of the shavings. If that doesn't do it or if you have no known samples, then taste never fails to determine the 'oil taste'.

[Steve Barker]

since when can't you put latex directly over oil based paint? I've done that dozens of times.

[Roger Shoaf]

Sure it will cover but it will also peel off. Read the can or ask at the paint store.

[deke]

Actually it will NOT peel off.

Very rare for it to peel off.

[Steve Barker]

I've never had it peel off. I don't see how the latex could tell the difference. A clean , dry, hard surface is a clean, dry, hard surface.

[Norminn]

Latex will peel if put on over enamel and the surface not prepared correctly .. I've peeled off large sheets in fixing other folks' lousy work. If put on over enamel, it should be sanded and primed first, IMO. I never use latex on trim or doors because it is impossible to sand if another paint job is needed.