Polyurethane is one of the most durable finishes out there but like all paints, polyurethane is bound to chip and crack eventually. When this happens, can you paint over the polyurethane?
You can paint over polyurethane paint. But you’ll have to degrease, sand, and wipe the polyurethane before painting over it. This is to allow the paint to stick and dry properly.
You should know that it is easier to paint over water-based polyurethane than oil-based polyurethane. You should also know that a coat of stain-blocking primer over the polyurethane finish will make the paint stick and perform better.
But that’s not all. There is more to know about painting over polyurethane and this post digs right into the topic. Let’s dive in.
Will Paint Stick To Polyurethane?
Paint will not stick properly to polyurethane because polyurethane dries to form a hard and moisture-resistant film that will prevent the paint from sticking.
Generally, paint doesn’t stick to polyurethane. The reason for this is that polyurethane paint doesn’t have the requirements needed for the paint to stick. For paint to stick properly, the paint coating has to be able to bite into something.
This is why paints usually stick to porous surfaces like wood since the paint can bite into the wood. However, polyurethane doesn’t allow the paint to bite into it. This is because polyurethane is a moisture-resistant finish.
Being a moisture-resistant finish, polyurethane doesn’t allow moisture (oil or water) to penetrate or stick to it. Since all paints are either water-based or oil-based, the paint will not penetrate or stick to the polyurethane finish as well.
Also, polyurethane has a natural glossy top coat. This glossy top coat is slick meaning that if you put paint over it, the paint coating will most likely slide off the polyurethane coating. This also makes it very difficult for any paint to stick to polyurethane.
However, you can make paint stick to polyurethane if you sand and prime the polyurethane first. The sandpaper will remove some of the hard-polyurethane layers. This will make it easier for the paint to penetrate the polyurethane and stick. Also, the primer coating will create an undercoat for the paint to bite into making the finish smoother.
Can You Paint Over Polyurethane Without Sanding or Priming?
You can but you shouldn’t paint over polyurethane without sanding or priming. If you do, the paint will not stick properly.
Though the paint will stay on the polyurethane initially, it will start to crack and peel off after a few days. The cracking and peeling are due to poor paint adhesion.
As explained earlier, the purpose of sanding and priming before painting over polyurethane is to allow the paint to stick and come out smooth.
So if you paint over polyurethane without sanding or priming, the paint will not stick or come out smooth when dry. But that’s not all that happens if you paint over polyurethane without sanding or priming.
If you paint over polyurethane without sanding or priming:
- The paint will not adhere well to the surface and can be easily wiped off
- The paint will be easily affected by heat and moisture
- The finish will not be durable
- The paint will turn sticky or tacky
- It will be impossible to seal the finish
- You’ll eventually have to remove the paint and start all over
How To Paint Over Polyurethane? (5 Simple Steps)
This guide will show you how to paint over polyurethane in 5 easy steps but, you’ll need a few tools and supplies:
- Medium and fine-grit sandpaper
- A paint scraper
- Degreaser or cleaning solvent
- A paintbrush or spray gun
- An oil-based paint primer
- A gallon of paint
- A pair of gloves
- Breathing protection
- Wood filler (optional)
- A sealant or top coat
Here is a quick rundown of how to paint over polyurethane:
- Degrease and clean the polyurethane
- Repair and fill cracks in the surface
- Sand the polyurethane
- Apply two coats of paint primer
- Apply up to 3 thin coats of the paint
- Seal the paint (optional)
Now, let’s get to work.
1. Degrease and Clean The Polyurethane
The first step is to degrease and clean the polyurethane finish. If the surface is dirty, then the paint will not come out smooth. Also, grease on the polyurethane can bleed through the paint and ruin the finish.
To degrease the polyurethane, you can use a degreaser like TSD (Trisodium Phosphate) or a cleaning solvent like vinegar or white spirits.
Pour some of the solvent on a clean cloth and use the damp side of the cloth to dab the polyurethane. Ensure to cover every area of the polyurethane. Then leave the degreaser for about 5 minutes to work. After 5 minutes, use a dry rag to wipe the degreaser and the stains off the polyurethane.
2. Repair and Fill Cracks In The Surface
It’s unlikely that you’ll find cracks or holes in a polyurethane-coated item but if there are any cracks or dents, you should repair and fill them. If it’s a wooden item, fill the cracks and holes with a wood filler.
You can also use caulk on items like plaster, drywall, and wood trim. For concrete and masonry, use concrete paste.
3. Sand The Polyurethane
Sanding will go a long way in ensuring the paint sticks well and the finish comes out smooth. To sand, start with medium-grit sandpaper. Use 150-grit to kickstart the sanding.
The medium-grit sandpaper will remove stubborn stains and dust nibs. Then finish off with fine-grit sandpaper. Fine-grit sandpaper like 220-grit will even out grain and smoothen the surface.
While sanding, don’t press too hard on the sandpaper or you’ll ruin the polyurethane. After sanding, wipe off the dust.
4. Apply Paint Primer
Just like sanding, priming also helps to improve the finish. You need just a coat or two thin coats of paint primer on the polyurethane. It’s generally advised to use an oil-based primer over polyurethane. This is because polyurethane has a high level of solvents and oils that will be compatible with an oil-based primer.
You can apply the paint primer using a paintbrush. Ensure to allow enough dry-time between coats. When both coats are fully dry, you can apply the paint. It will take about an hour for the oil-based paint primer to dry.
5. Apply The Paint
It’s better to apply the paint using a spray gun. This way, you can apply the paint faster, get more coverage, and avoid brush marks. You should know that the paint has to be well-thinned to be sprayed. You only need 3 thin coats of paint on the polyurethane. You should allow enough dry-time between coats.
Since you used an oil-based primer, it is better to use an oil-based paint as well. Enamel paint is known to work well on polyurethane plus enamel paint is strong and durable. You can also use a water-based paint over the oil-based paint primer. But, you should ensure that the primer is compatible with water-based paints.
6. Seal The Paint (Optional)
This step is optional but a sealant over the paint will make the finish last longer. You can use gel stain, lacquer, wax, or any other sealant over the paint. Ensure to leave the finish for at least a day before sealing it.
Now, let’s check out some popular paints and see if you can paint over polyurethane with them.
Do You Have To Remove Polyurethane Before Painting Over It?
You don’t have to remove polyurethane before painting over it. As long as the polyurethane finish is still in good condition, all you have to do is sand the polyurethane and then apply a coat of paint primer to allow the paint to stick better. You should only remove the polyurethane if it is defective.
For instance, if the polyurethane paint is wet or peeling already, you should remove it before painting over it. Also, if the polyurethane is oil-based, it’s a good idea to strip the top glossy layer before painting over it.
This is because oil-based polyurethane is usually harder than water-based polyurethane and as such will be more difficult to paint over. So the best bet is usually to remove the oil-based polyurethane first. Water-based polyurethane doesn’t need to be removed.
The reason it is usually advised to remove polyurethane before painting over it is to get rid of the top layer of the polyurethane so the paint can stick well. But you don’t always need to remove the entire polyurethane coating. You only need to remove some of it to allow the paint to bite and stick well.
You can also carry out a process known as “stress sanding” This is a method of preparing the polyurethane where you only sand the areas that will experience heavy use.
For instance, on a polyurethane-coated desk, the stress areas will be the tabletop and the edges. These are the areas that will see constant use and where the paint is most likely to come off first. So you need to ensure proper paint adhesion in these areas.
When you sand the stress areas, the paint will stick and become stronger so it’s less likely for the paint to come off even when you didn’t remove the polyurethane first.
Different Types of Paint To Use Over Polyurethane?
Here are some different types of paint that you can or can’t use over polyurethane:
You can paint over polyurethane with chalk paint easily. This is because chalk paint has very impressive adhesive qualities meaning that chalk paint will stick to just about any surface including polyurethane. But you’ll need to sand the polyurethane before putting chalk paint over it.
You should know that chalk paint is water-based so the paint primer to be used must be compatible with water-based paints. Chalk paint is also thick so to spray the paint, you’ll have to thin it with equal parts of water.
You can paint over polyurethane with enamel paint since enamel paint is an oil-based paint.
However, it’s very necessary to prime the polyurethane first. Since enamel paint is oil-based, it would glide off the glossy layer of polyurethane. So you need to cover the polyurethane with a primer to allow the enamel paint to stick.
You can paint over polyurethane with latex paint. Latex paint is flexible so it will cope with the polyurethane very well.
But you’ll need a paint primer before the latex paint can stick because latex paint is water-based and it won’t stick to the glossy top coat of polyurethane.
Some spray paints can go over polyurethane. Spray paints are known to contain different types of chemicals and additives. Some of these chemicals will not stay on polyurethane. For instance, spray paints that have high levels of silicone will not stick well to polyurethane paint because silicone repels paints.
So before you put a spray paint over polyurethane, ensure to check if the spray paint can be used over polyurethane sealant. Spray paints that contain urethane will work perfectly on polyurethane.
Acrylic paints can be used over polyurethane. But, like all water-based paints, you’ll need to sand and prime the polyurethane paint first to allow the acrylic paint to stick.
You should ensure that the acrylic paint to be used can be used over polyurethane because some acrylic paints also contain additives that wouldn’t go well on polyurethane paint.
You can paint over polyurethane with milk paint. But, it’s better to paint over water-based polyurethane with milk paint. This is because milk paint is basically water and color.
The paint doesn’t have binders and adhesives in its formula and as such wouldn’t stick well to oil-based polyurethane. You should also know that milk paint is not known for its durability. So ensure to seal it with a protective sealant to prevent the finish from chipping.
Related Read: Can You Apply Polyurethane Over Old Polyurethane?
Overall, you can paint over polyurethane. Though the paint is commonly used as the final coat, it can be a basecoat too. All you need to do is to degrease, sand, and wipe the polyurethane to allow the paint to stick properly.
Also, you don’t need to remove the entire polyurethane coating to paint over it. You just need to sand the stress areas to give the paint good durability.