How to Paint Latex Paint Over Oil Based Paint

A lot of people think that you can’t paint over oil-based paint with latex paint, but with the right tips, tricks, and techniques you can. The issue with painting over oil or alkyd-based paint is that it as it dries it presents a very slippery surface. Oil paint continues to cure as it dries, and this process goes on almost indefinitely. A lot of older homes were painted with oil-based paint, as it wasn’t until the 1970’s that latex paint really came into its own.

The key to getting latex paint to stick to oil based paint is, like most things with painting, preparation. It is important to take the time to properly prepare and prime the surface before you go about painting it. In this article we will take a look at the techniques you can use to prep the surface for a professional finish.

Before you begin to do any surface prep you will need to ensure that you are actually dealing with an oil based paint. While you can pay for a commercial test there is a much simpler way to check. You can use fingernail polish remover, denatured alcohol or lacquer thinner to coat a q-tip. Rub the q-tip in an inconspicuous area and take a look at the tip. If you have latex paint, then some of the color will come off on the q-tip. If you have oil based paint on the walls nothing will happen. Latex paint is also usually gummy to the touch, and this is another clue as to what type of paint you are dealing with. One important tip is to make sure that if you decide to use fingernail polish remover for this test, that the remover contain acetone as an active ingredient. Some fingernail polish removers are acetone free, and those products will not work for this test.

The next thing to do is to make sure that the walls are clean and prepped to accept a new primer coat. The way to do this is to sand the walls lightly with a high grit sandpaper. You can use a drywall-sanding pole to make this job go easier, since you will be sanding a large area. Remember you are not trying to remove the paint, you are only trying to scuff the surface, so that you can make it accept the primer better. As you sand you will create dust. After you are done sanding you will need to remove this dust and clean the surface. The way to do this is to go over the walls with a shop vac, if you find that it is really dusty. When finish you should rub the walls down with a tac- cloth. Tac-cloths are cloths, which have a special tacky substance sprayed on them and dust sticks to it very well.

Now that your walls are prepped – you are ready to apply the primer coat. This is the real trick to getting the latex paint to stick. While it does seem like an extra step, and a lot of extra work, priming is key. You can use any type of latex primer but I recommend Kilz. Kilz is great not only because it is an excellent primer, but also because it acts as a stain sealer. For example I once worked on a project where there was one wall in the room, which was coated with an oily stain. One coat of Kilz and I was able to block the stain and finish the project.

Once the primer coat has dried you can go and paint the wall with any good latex paint as you normally would. It might take more than one coat, as the primer coat can sometimes be a little thirsty for paint. The sanding step of this project may have also scuffed the surface where it may call for an extra coat just to give an even professional finish.