How to Identify Latex Paint on a Surface Finish

Distinguishing between oil-based and latex paint is important before repainting.

Latex paint was not available until the 1960s. Oil-based paint was originally made with linseed oil; modern oil-based paint is made with synthetic or alkyd-based oil. Oil-based paint generally provides a smoother application with less stickiness but latex paint is considered better for the environment and dries quicker than oil-based paint, and you can clean it up with soap and water. If your house was built after the advent of latex paint in the 1960s, you will need to determine if it was painted with latex or oil-based paint before proceeding with any repainting projects.

Things You'll Need

• 1 tablespoon detergent
• 1 cup water
• Cloth
• Denatured alcohol or nail polish remover

Instructions

1. Mix a tablespoon of detergent into a cup of water. Dip a cloth into the detergent solution and scrub onto a small area of the painted surface.

2. Dampen a small cloth with denatured alcohol or nail polish remover and rub the painted area vigorously. Examine the cloth for paint residue. If any paint comes off, it is latex. If there is no residue, you're dealing with oil-based paint, which will not rub off. Place your hand over the area; if it feels tacky or rough, it most likely has latex paint.

3. Consult an expert at a paint or hardware store to determine the best way to proceed with any repainting project. Generally, you can apply latex paint over oil-based paint but you should not apply oil-based paint over latex paint since it will not adhere well.

Tips & Warnings

• When painting the exterior of a house, it is advantageous to use latex paint because the resins in latex are often too large to seep into microscopic holes in the wood. The gaps between the larger particles in latex paint allow water to pass through, making latex paint less likely to peel due to interior moisture problems in the house.

• When applying latex paint over a surface previously coated with oil-based paint, you will get the best results if you first sand and then prime the area with a latex-based primer. However, it is possible to apply latex paint directly to an oil-painted surface if the oil-based paint is less than 1/16 of an inch thick (the equivalent of 16 to 30 coats).

References

• Painting Tips & Tricks: Do I Have Latex or Oil?
• This Old House: Why is My Paint Peeling?

Resources

• New Hampshire Department of Environmental Services: Latex Paint