Latex or oil-based paint: which one belongs on your walls and trim

What the names mean today

"Latex" is the everyday word for water-based paint, and you'll often see "acrylic" on the label too. "Oil-based" is a little loose as well. Dunn-Edwards points out that a true oil paint is something only your grandfather or great-grandfather would have used. Those gave way to synthetic resin paints called alkyds, which are only partly oil. Benjamin Moore puts it plainly: conventional alkyd paint is an oil-based paint.

So when a can says "alkyd" or "oil-based," it's the same family. When it says "water-based," "latex" or "acrylic," you're in the other one.

Latex and oil side by side

The drying and cure times are from a Dunn-Edwards bulletin, and they shift with temperature, humidity, color and how thick the coat goes on. Latex cures as the water leaves and the particles fuse into a film. Oil-based paint hardens by reacting with oxygen in the air, which is why it keeps getting harder over time. Our post on paint dry time versus cure time explains why "dry" and "ready" aren't the same thing.

Makers don't all give the same numbers. Benjamin Moore puts a conventional alkyd at about five days to a hard finish, a bit faster than the Dunn-Edwards figure. Treat the table as a pattern, not a promise: oil-based paint dries more slowly, then hardens by a different route.

Why oil-based paint is still around

The finish. Benjamin Moore says conventional alkyd cures to a hard, glossy surface that latex can't quite match, which suits interior trim, doors, cabinets and other high-use areas. A brushed coat flows out so smoothly it can look sprayed.

The costs are real, though. Conventional alkyds use petroleum-based solvents, carry higher VOC levels and need paint thinner for cleanup. Our post on low-VOC paint explains what those numbers mean and what to do about fumes.

There's a middle path too. Waterborne alkyds are paints with the flow and leveling of oil-based paint and soap-and-water cleanup. Benjamin Moore says its waterborne alkyds fully cure in approximately five days, against three to four weeks for latex acrylics.

They're not a drop-in swap if you've only ever used latex. Benjamin Moore warns there's a learning curve, because waterborne alkyds are less viscous, and suggests testing a small area before you commit to a whole door or cabinet. Our post on which paint type suits kitchen cabinets sets waterborne alkyd beside acrylic enamel and oil for cabinet work.

Painting latex over oil-based paint

This is where most failures happen. Old oil-based enamel gets harder and slicker over time, and water-based paint doesn't wet it well. Dunn-Edwards compares repainting it to painting glass. The National Park Service explains the mechanics in its guidance on paint problems: oil paint keeps hardening with age, and the shrinkage of a new coat drying puts stress on it, so latex applied straight over old oil paint is more apt to fail.

It can be done, and it comes down to prep. This is the order that works:

1. Confirm what's there. Rub a cotton ball soaked in rubbing alcohol over the paint. If some paint comes off on the cotton, it's latex. If not, it's oil-based.
2. Clean off cooking grease, fingerprints, nicotine and anything else that could keep new paint from sticking.
3. Sand the gloss dull. Dunn-Edwards says scuff-sanding isn't enough; the surface should end up essentially flat.
4. Wipe away the dust and prime. For latex over oil, the Park Service recommends an oil-base primer first.
5. Apply the topcoat, and expect two coats.

That's the same sequence we use for trim and doors on an interior painting job: clean, sand, repair, prime, then paint. Our guide to painting trim walks through the DIY version, and do you need primer covers which one to buy.

Cabinets, banisters and other classics

Dunn-Edwards names the classic oil-based surfaces worth saving: a worn banister, original cabinetry and other architectural details in older houses. Its advice for anyone considering replacing them is to repaint instead, and to treat prep as the main event.

That matches how we work. On every cabinet refinishing job, the cabinets are cleaned, degreased, sanded and primed before any paint goes on, and the doors and drawer fronts are sprayed. Our guide to painting oak cabinets shows what that prep does for a grainy surface.

Painting oil-based over latex

The reverse can fail too. The Park Service notes that oil paint applied over latex can peel, because as it ages the oil paint becomes harder and less elastic than the latex underneath it. If you want an oil-based finish over a latex surface, sort out the prep and primer before you buy the can.

Older homes and old trim

Older homes add one more consideration. EPA reports that about three-quarters of the homes in the United States built before 1978 still contain some lead-based paint, and its Renovation, Repair and Painting rule sets lead-safe work practices for paid work that disturbs painted surfaces in those homes. Sanding old woodwork is exactly the kind of work that disturbs paint, so mention your home's age when you call.

Whatever the age, leftover paint and thinner need proper disposal. Our post on how to dispose of paint in Dane County covers where it goes.

Which one to choose

• Walls and ceilings: latex. It dries fast, cleans up easily and has lower VOC levels.
• Trim, doors and cabinets: oil-based or waterborne alkyd if you want the hardest, smoothest finish, or a latex enamel if you want the simplest job. The surface and what's on it decide.
• Over old oil-based paint: either stay with oil, or do the prep above and prime for adhesion.
• Anywhere you'll be wiping and washing: the sheen matters as much as the paint type, and our guide to paint sheens shows how to pick one.

You don't have to settle this alone. Interior painting is priced by the square footage of the space, with paint included, and George can tell you on the estimate call what he'd suggest for your trim and doors.