oil or latex. Generally speaking, oil-based paint can be painted over latex, but latex will not adhere to oil-based paint. For this reason, the type of paint you need to use or the prep work will depend on the paint that is already there. Fortunately, there are a few ways to easily find out.
The Alcohol Test
You can perform a simple test to find out if your walls and trim are oil-based or latex paint. You need warm water, soap, and alcohol. Start by washing a spot on the wall or trim with the warm water and soap. You can use a sponge or a soft cloth, and once you wash it, rinse it off. Wait for it to dry, and then soak a cotton ball in the alcohol. You can rub the cotton ball back and forth over the clean spot to see if any paint comes off. If the paint comes off, it is latex paint. If you are unable to remove any paint, it is oil-based.
Painting Over Old Paint
If you have oil-based paint, you will not be able to paint over it with latex. The latex paint will not adhere very well, and it will end up chipping off or peeling. If you want to paint the walls or trim with latex paint, you will either need to remove the oil-based paint or you can sand the walls or trim and apply a bonding primer. Choose one that can go over oil-based paint. The primer, unlike the paint, will adhere to the oil-based paint, even if it is a water-based primer. Once you allow the primer to dry, the latex paint will adhere to it when you paint.
Should You Use Oil-Based Paint?
Most people use latex paint indoors, and some states do not allow you to use oil-based paint indoors. Oil-based paint is often used on exteriors of buildings because it is known to be more durable. It is also a lot more difficult to clean up because you need turpentine or another paint remover, whereas with latex paint, you only need soap and water.
Oil-based paint is often used for high-gloss items, cabinetry, doors, and trim because it is more durable and lasts longer. It takes longer to dry, but it holds its sheen longer. Latex paint dries more quickly, and it is a great choice if you like to change the colors more frequently.
When you want to paint your walls or trim, you need to know if the paint is oil-based or latex. Luckily, you can easily perform a test with alcohol to find out. If the paint is oil-based, you will need to strip the walls and trim to paint with latex, or you can sand it and apply a bonding primer.