First, make a solution of detergent and water to scrub the test area. Take a cotton swab, and rub rubbing alcohol over the area. If the paint peels, it is latex.
Acetone is another alternative for testing paint. Testing the base of the paint determines the longevity of a new paint job. Both types have different properties. If the paint is latex, a latex paint must be used for a new paint job. Painting oil over a latex paint causes the new coat to crack. Oil paint requires a primer before a new paint job. If latex is painted over oil paint, the latex paint peels off.