How to Determine if Paint Is Latex or Oil Based

Painting the exterior of your house is a big investment in time and materials. Choosing the color is the fun part, but you need to know if the existing paint is latex or oil based. If your house is already painted with latex paint, you'll need to repaint with latex paint. Putting oil-based paint over latex paint is not recommended for exterior surfaces because the oil-based paint does not adhere well to latex. If your house currently has oil-based paint on the exterior, you may repaint with either oil based or latex.
If you're painting an interior surface, you may apply oil based or latex paint over one another with no compromise in quality or performance.

Difficulty: Easy

Instructions

Things You'll Need:

• Denatured alcohol Cotton balls or soft cloth

1. Look at the surface of the paint. Latex paint will show marks from the roller or brush used to paint the surface. Oil-based paint shows very few, if any, brush or roller marks.

2. Touch the paint. Try to dent the paint with your fingernail. Latex paint will dent easily with your fingernail. Oil-based paint is harder and will not dent as easily.

3. Remove a chip. If the paint has peeled away from the wall, remove a chip and test it by bending it between your thumb and finger. Latex paint will bend but not break. Oil-based paint will snap easily.

4. Try chemistry. Put a small amount of denatured alcohol on a cotton ball or soft cloth. Rub the cloth over a small area of paint. If the paint comes off onto the cotton or cloth, or if the surface of the paint becomes tacky, it is latex. If no paint appears on the cloth and the surface of the paint remains unchanged, it is oil based.

Tips & Warnings

• If you still can't determine if the paint is latex or oil based, before you repaint the surface, sand lightly, clean off sanding residue and prime with a primer appropriate for the type of paint you plan to apply.