Painting your home’s interior is a huge task and should not be taken lightly. However, you might be OK if you have the time and are willing to learn a few trade tricks, like our painting over oil based paint.
However, if the job is too big for you, call the professionals and find a good, local interior painter.
In this article, we’ll explain tips for painting over oil-based paint and why applying latex directly to oil paint is bad. (Spoiler Alert: This is a much bigger blunder than it sounds.)
What is latex paint?
The one question we often hear is, can you paint latex over oil? The short answer is no. The longer answer is also no, but that would make for a concise blog article and leave you without the help you need.
And suppose you ignore this warning or don’t have the advantage of seeing an article like this beforehand. In that case, you’ll recognize almost immediately after finishing that you made a huge mistake and one that will cost you much more time and money.
Latex paint is a general term used for water-based paint, so consider them interchangeable with acrylic latex paint. Latex paint consists of pigment and a binder and uses water as the carrier.
Oil-based paint consists of particles of pigments suspended in oil, often linseed oil. It also has an organic solvent (usually mineral turpentine) as the carrier. People may refer to oil-based paint as enamel paint, but this must be corrected.
They behave and perform quite differently because they each have such different compositions. This applies to painting your home’s interior and cleaning or maintaining the walls and trim. And it matters a great deal when painting over oil-based paint with latex.
How to test if it is latex or oil paint
Since applying latex or water-based paint directly over oil-based paint is such a disaster, you’ll want to test the color currently on your walls first. And this is relatively easy to do.
All you need for this test is denatured alcohol and a few clean rags. Apply a little alcohol to a rag and begin wiping the painted surface.
What do you notice? Does the paint appear to be coming off., Or is there little to no effect?
Denatured alcohol will remove latex paint but not oil-based. If there is no effect, you’ll know it’s oil-based.
If you fail this test, you will notice some unmistakable signs that a mistake was made. Your newly painted wall will appear wet and splotchy, and the paint will peel off very easily using just your fingernail.
Why applying latex directly to oil paint is a bad idea.
That wet and splotchy appearance (some compare the look to a fruit rollup) is that latex paint cannot adhere to oil-based paint. Because the two are incompatible, they will never form a good bond, so latex paint peels off so easily.
This is especially true for gloss or semi-gloss oil-based paints.
The big problem is that you may only notice your mistake once your work is finished. You can assume that the latex paint is wet and drying slowly. But when you clean up and remove your painter’s tape, you’ll wonder why it’s taking so long. And why it doesn’t look quite right.
That’s a lot of work and money down the drain, and now you have to begin all over.
The solution is simple: Apply an oil-based primer. You only need to add one step to avoid this mistake. And for your sanity, better if you do it on the first attempt.
What is an oil-based primer?
Oil-based primer is simply a primer that uses oil as its base. Oil-based primer is excellent for sealing in stains and tannins. So, if you have a nasty stain or smell that you’d like to cover, oil-based primer is ideal.
And remember, oil on top of oil adheres well. For our purposes, that is the biggest reason to apply a coat of primer on top of your oil-based paint before repainting with latex.
On a side note, if you’re wondering if you can apply an oil-based paint over top of oil-based paint, the answer is yes. However, if they’re dirty, you’ll still want to use a solvent or cleaning solution to wipe the walls down first.
You might also find tape, large nail holes, and various debris on your walls and trim during this process, so better to deal with it now instead of when you’re holding a roller in your hand.
Why should I use latex paint over oil primer?
When using latex to start painting over oil based paint, you only need to add this extra step if applying latex or water-based paint to a surface previously covered in oil-based paint. And the reason is simple: It won’t work otherwise.
At the very least, it will look not very good and not last very long, unlike a professional interior paint job that’s simply stunning.
For those of you trying to decide between using latex paint or oil-based, latex does have a few advantages:
1. Latex paint dries faster.
Water-based paint dries much faster than oil-based paint. The first coat will usually feel dry after 30 or 60 minutes. With oil-based paint, you’re looking at between 6 and 8 hours. That’s a lot of extra time to keep kids and pets from accidentally coming into contact with your newly painted surfaces.
The fast drying is due to the water component of the latex paint. Water evaporates, leaving the paint to dry much faster than the thicker, oil-based paint.
2. Latex paint doesn’t turn yellow.
If you want your white walls to stay white longer, latex paint is the way to go. White latex paint won’t yellow over time, while oil-based paints are prone to yellowing. This yellowing concerns the chemical compounds in oil-based paint that cause a color-changing reaction over time.
You’ll avoid this yellowing issue since latex paints don’t use these chemicals.
3. Latex paint uses less VOCs.
Volatile Organic Compounds (VOCs) are organic solvents in vapor form. Some VOCs are toxic and even carcinogenic, as in cancer-causing, but many of them have the potential to impact your health negatively.
As the paint dries, these vapors and gasses are released. Because the drying component in latex paint is water, fewer VOCs are released.
To put it, this means that latex paint is better for your health but also much better for the environment.
4. Latex paint is more flexible.
If durability is necessary, oil-based paints are great as they dry very hard. However, this makes oil paint much more prone to cracking. Latex paint, on the other hand, dries softer and remains more flexible. This results in less flaking and cracking.
5. Latex paint is UV resistant.
This would mainly apply to your exterior paint. However, if your interior walls and trim have direct sunlight hitting them during the day, it could also affect your interior paint. What effect does UV have on oil-based paint?
Oil-based paint does not perform well when exposed to UV light, as it begins to break down and develops a chalky surface. Latex paints don’t have this problem and will retain their shine and color over the long haul much better than oil-based paints.
Tips on placing latex over oil primer
Before we get to the tips for painting over oil based paint, there are two other options besides using an oil primer, and they are:
1. Sand the entire surface
The glossy, smooth surface prohibits latex from adhering to oil-based paints. If you sand all that away, you’ll be ready. You’ll want to use 220-grit sandpaper for this, and be careful around protrusions or inside nooks and crannies, as you specifically find with trimming. This is where an oil-based primer becomes easier to work with.
2. Apply a chemical deglosser.
Applying a chemical deglosser is like waxing your car. Put a little on a clean rag and wipe it aggressively across the surface. (Perhaps more aggressive than you would with your automobile.) Once dry, your walls should have a smooth, dull appearance.
Now to the Tips on placing latex over oil primer
Here are our top 7 tips for painting over oil-based paint
Tip #1: Create a smooth surface
Oil-based primers take 8 hours to dry, and you can lightly sand over the primer to make the surface as smooth as possible.
We recommend using 180-grit sandpaper to create a better bonding surface for your latex paint. Cody Hartrum
When you’re done sanding, remember to wash away any dust caused by the sanding and allow the area to dry. This is also an excellent time to fill holes or gaps using a wood filler or putty.
You want the surface to be as smooth and dry as possible.
Tip #2: Clean the surface
After you let the surface dry completely, use a clean cotton cloth to wipe it down. You can also use a tack cloth ‒ an inexpensive cheesecloth with beeswax added to it.
The sticky surface of the tack cloth works well for removing any loose dirt that might still be on the surface. Keep the pressure to a minimum when wiping down the surface, as you don’t want the wax to come off the cloth and onto the surface.
This tip is essential if days or weeks pass by between priming and painting.
Tip #3: Take it slow and wet
Now that you have a smooth, clean surface, it’s time to begin painting.
Put only a little paint on the brush and begin with slow, even strokes. Keep a wet edge on the brush at all times as you paint. And only use a high-quality paintbrush to get the best results.
Wait a couple of hours before applying a second coat.
Tip #4: Get proper ventilation
This tip won’t affect your paint job unless you pass out while holding a whole paint can. But it can protect you from a future headache or worse. Consider opening a few windows and turning on a fan to circulate the air. Or maybe wear a paint respirator.
Tip #5: Rough up the surface before priming
One of your goals when applying latex over oil is to get that glossy sheen off the surface. This is what can trip up your hard work. And to do this, consider sanding the surface before applying an oil-based primer.
We recommend using 100-grit sandpaper for this and feel free to use an electric sander if you have one. Sanding allows the primer to adhere better, as does using coarser sandpaper.
Tip #6: Use a sealer for old surfaces
A sealer paint goes on before your oil-based primer, but most of you probably won’t have to bother with it. However, if you’re dealing with an old surface (or porous substrate) that is unfit for painting, you may want to add this extra step.
A sealer paint provides better adhesion for the primer that comes next. Just make sure to find a sealer specifically for latex paint. Usually, a thin layer is all it takes.
Tip #7: Hire a professional
Painting over oil based paint can produce long-lasting and robust results if you know what you’re doing. And as you can see from this article, painting an interior is never as easy as just applying a coat of paint.
If you live in or around St. Louis and would like a free estimate, fill out our free estimate form today! We proudly service many cities across St. Charles County, St. Louis County, Jefferson County, and Franklin County.
HBP Painting Contractors has a large service area across the St. Louis Metropolitan area. We offer full-service interior and exterior painting for residential & commercial customers. Our #1 priority is to provide you with an exceptional painting experience.
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