Water And Oil Don’t Mix: How To Paint Over Oil-Based Paint


by Houston Texas Painters - July 28, 2021

Oil and water don’t mix. And this also applies to paint! Decades before, oil paint was the way to go for house painting. Currently, new high-quality latex and other water-based paints are the top choices for DIY home projects. The challenge is that you can’t just paint over oil-based paint!

Before refreshing the looks of your home with a new coat of paint, learn how to paint over oil-based paint!

You are not sure if it’s oil-based paint? Run this test! 

Unless you painted the surface yourself, you might not know what type of paint was used on the wall or surface. However, you can run this quick test and make your conclusions: 

  1. Rub the painted surface with a cotton ball or pad dipped in denatured alcohol. 
  2. If the cotton ends up stained in paint, it is water-based. On the contrary, if the paint doesn’t rub off, it’s oil-based.

You are not sure how to prepare your room for painting? Check our complete guide!

How to paint over oil-based paint

You can paint over oil-based paint, but only if you are using another oil-based paint. The problem comes from the fact that water-based won’t bond well to glossy oil paint. 

Does that mean you have to stick just to oil-based paints? Not really! Latex and other water-based paints are becoming the popular homeowners choice, as they dry faster and are gentler to the environment. However, you need to sand and prime the surface first! 

Learn how to paint over oil-based paint below!

Step 1. Sand the gloss off the oil paint

What happens if you use water-based paint over oil-based paint? The new coat of paint will peel off in less than a month! Think of the painted surface as a recently waxed shiny floor: the new coat will just slip off from the glossy oil paint!

First, you have to remove all the sheen!

  • Before starting, wear a mask to avoid inhaling the fine particles!
  • If the paint is already cracking, remove the chips with a putty knife.
  • Use fine-grit sandpaper (between 180-220) for slightly sanding the entire surface you will paint. Keep sanding until the paint is no longer slick and glossy, but be careful not to scrub or remove the paint. 

Step 2. Clean the surface with TSP

The coat of paint will adhere properly only if the wall or surface is squeaky-clean. Use trisodium phosphate diluted in hot water to wipe your walls before painting!

  1. Dress in your protective gear! Rubber gloves and protective goggles are a must when handling TSP.
  2. Mix a gallon of hot water and ¼ cup of TSP powder in a bucket. You’ll need another bucket too, but only with hot water.
  3. Dip a sponge in the mix and wring it well. The sponge should be only damped!
  4. Starting on the bottom of the wall, wipe a section (about 2-3 square feet) with the damped sponge. Wait for about two minutes to let the solution work, and then scrub the section again.
  5. Rinse each section with a clean sponge and plain hot water before moving on to the next. 
  6. Wait until the surface air dries completely.

This powerful cleaning product washes grime, fingerprints, and grease from your walls. Also, it will remove splintered or flaked paint that otherwise would prevent paint adherence.

Step 3. Prime the walls

Primer helps the new coat of paint grab onto the surface smoothly, but it also covers any imperfection. 

Use a high-quality bonding primer and add one or two coats and wait until it dries before starting to paint. The drying time depends on the product you are using:

  • Water-based primers usually take less than one hour to dry completely. 
  • Oil-based primers can take up to 4 hours!

Pro-Tip:

Houston’s temperature and humidity during your painting project might also affect how fast the prime dries. Check the forecast and pick a warm day between 40%-70% humidity.

Step 4. Paint at least two coats

Now you just have to roll on that paint! After following the previous steps, paint should adhere nicely to the surface. Adding two coats of paint at least will give it a smooth color and finish! 

However, make sure to follow the mixing and drying instructions of the latex or acrylic paint you are using. 

Professional painters in Houston

Painting projects need attention and care to produce the results you imagine. If you want to skip the hassle and enjoy the results, give Houston Texas Painters a call! Our contractors are fully insured and experienced in all kinds of painting projects and remodeling jobs. 
Ask for your free estimate today!