Is My Paint Latex Or Oil?

Many people ask how to determine if the existing paint on their walls/ceiling/trim is oil or latex.

Latex paint shows more brush strokes and roller stipple than oil, and can usually be dented with a fingernail very easily.

Oil dries to a much harder, brittle surface, is usually very smooth/glossy, & shows hardly zero brush or roller marks. It also can't be easily dented with a fingernail.

For the real test:

Take a rag, or Q-Tip for smaller spots, and dip it into some denatured alcohol. Rub it into the paint. If the paint comes off onto the rag, or smears, or appears to melt, its latex or another water-based product. If it remains solid, it is an alkyd, or oil product.

You can also use 'Goof Off', or 'Oops' to try this, but the results won't be noticeable as fast.