Oil and latex are the two most common paint varieties, each best suited to certain materials and conditions. However, mixing them can result in peeling paint, color shifts, or worse.
Knowing how to tell if paint is oil or latex is an essential DIY skill. Read this guide to learn how it’s done.
Oil-Based Paint: Features & Characteristics
Coloring pigments are suspended in oil to create oil-based paint. Linseed oil and synthetic compounds like alkyd and acrylic are the most common binders, while solvents like turpentine or white spirit are used as thinners to keep the paint at a usable viscosity that's reasonably close to the color it will have once it dries.
Oil-based paint traditionally has more sheen and a thicker consistency, although manufacturers are now achieving shinier finishes and a higher viscosity in water-based paints as well. The finished look of oil-based paints is still known for its gloss and deep coloring.
Durability is one of the standout features of paints with an oil base. They can handle routine contact and harsh conditions, which is why they’re frequently used for painting exterior walls and trim in high-traffic areas. Plus, they give off lots of fumes that can be dangerous indoors without proper ventilation.
Paint thinner or turpentine is necessary to clean up oil-based paint. Expect a longer drying time than you would with water-based paint. Because oil-based paint doesn’t let air through, it’s great for preventing rust and oxidation on metals. It also works on concrete and vinyl siding.
Latex Paint: Features & Characteristics
Water-based paints are created from water-soluble resins like gum arabic, organic solvents like hydrocarbon, and synthetic plastics. In the old days, these paints were made with rubber as a binder, which is why we refer to them as latex paints.
Manufacturers have been able to create latex paints that have the gloss and coloring previously only achievable with oil-based paints. Latex paints can come in flat, satin, semi-gloss, or full-gloss finishes, among many others. DIYers choose latex paint for interior paint projects, particularly on materials like wood and drywall and on broad surfaces like walls and ceilings.
Water-based paints like latex are easier to clean up with nothing but water. They don't produce the hazardous fumes oil-based paints do, plus latex will dry in as little as an hour, while oil-based paints could take as long as 24 hours.
Since water is the carrier rather than synthetics or expensive oils, latex paints tend to be cheaper than oil-based paints. Latex paint is typically thinner right out of the can. You use plain old water to thin it for your paint sprayer rather than the paint thinner required for oil-based paints.
How To Tell If Paint Is Oil Or Latex? (Easy DIY Test You Need To Do)
You need to know how to tell if paint is latex or oil-based to be sure your new paint job will stick and hold on for more than a few months or a year.
There’s no foolproof way to tell the difference just by eyeballing the paint on the wall, but if your paint is still in the can, there are some simple ways to test if paint is oil or latex. If you can’t find or don’t trust the label, use one of these quick tricks to test whether your paint is latex or oil-based:
Oil-based paint has a distinctive smell from its ingredients. Take care not to run around taking big whiffs of paint and giving yourself brain damage - wear a respirator if you’re handling paint and determine whether fumes are present by wafting toward your nose.
Test It With Paint Thinners
Take a small sample of the paint and mix it with water or paint thinner. Combining latex paints with a paint thinner will more than likely cause the pigment to separate, creating a useless mess. Water in oil-based paint will also cause separation.
If you use water and the paint thins without issue, that’s a latex or other water-based paint. If the thinner works, it’s oil-based.
Wait For The Paint To Dry
Paint some of it onto a sample surface like wood or spare drywall. If it’s not dry within an hour or two, you’re almost definitely working with an oil-based paint.
How To Test If Paint Is Oil Or Latex
If the paint is already up on the wall, you can sometimes tell what kind of paint it is by the layers as you sand through them. When one layer sands out into dust, that’s great - if you get to goopy paint, that means someone tried to take a shortcut by mixing paint bases. You need to sand through the bad layer, even if it’s all the way to wood, before you can prime and add your coat.
Here’s how to determine if paint is oil or latex without sanding:
- 1Get some warm water, a sponge, and some soap.
- 2Find an isolated sample spot on the surface and wash it gently with the warm water and soap.
- 3Let it dry, then get a cotton ball with some denatured alcohol on it. Rub the sample spot.
- 4If the paint comes off, it’s oil-based. If not, it’s latex.
Chipping or flakes are a dead giveaway that somebody put oil paint over latex paint. While some people swear you can pop latex over oil-based paint with no problem, it typically leads to abnormal sagging or splitting after a couple of years, so if you see anything like that on the wall, you're dealing with shoddy paint or mixed bases.
People Also Ask (FAQs)
How can you tell if paint is water-based or oil-based?
Wet paint can be tested with a sample mixture of thinner or water or by painting a sample and seeing how long it takes to dry. Paint on the wall can be tested with the alcohol-swab method described earlier in this guide.
What happens if you paint latex over oil?
Applying latex directly over an oil-based paint will create a shoddy bond and lead to cracks or peeling over time. You can use an intermediary primer, or if there's no lead risk, sand through the paint, prime, and then put on your latex paint.
Can you paint water-based paint over oil-based paint?
Water-based paint usually won’t bond with the glossy additives in oil-based paints unless you either use a primer specifically for that purpose or sand away enough of the oil-based paint that the gloss is completely gone. Always check for lead risk with a certified inspector if you plan on sanding through old paint.
Blending oil-based and latex paints will lead to cracking and peeling paint. It might be right away or two years later, but your effort is wasted in either case.
Use the tips and tricks in this guide to test if paint is oil or latex so your next paint job can look great and last a long time.