Oil paints used to be the dominant paint in the market however because of the toxicity problems associated with oil paint chemicals, they have fallen into disuse. In fact oil paints are no longer available except in special applications
Many older homes still have the original oil painted surfaces. The newer paints in the market do not readily adhere to oil paint and therefore they must be specially treated prior to painting.
Are you looking at painting your walls but you have no idea if the old paint was and oil-based paint? It is very important to determine the kind of paint currently on the wall surface to be painted prior to paint application.
There is an easy method to determine if the paint was oil-based or latex. First, wash a small portion on the wall surface with water and a mild detergent and let dry completely. Then, take a cotton swab and soak it in rubbing alcohol or nail polish remover and rub it over the cleaned area. If the paint comes off, it’s a latex paint. If not, your wall was painted using an oil-based paint.
If you want to paint over an oil-based paint always use and an oil-based primer over the entire surface before applying your finish coat.