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Refinishing old furniture pieces in your home can give them new life and a new look, and the easiest and cheapest way to do this is to paint them. However, what if those pieces of furniture are coated with polyurethane? Instead of removing the coating, you might want to learn and understand how to paint over polyurethane instead. This process can easily be applied, but it will take a lot of hard work to get the paint to stick properly. We will now take you through the process step by step, ensuring a perfect finish for your project.
Table of Contents
Polyurethane Surface Condition
Before you can start on your project, you need to assess the condition of the polyurethane finish, as this will determine the process you should follow. Painting over polyurethane, or painting over clear coat finishes for that matter, will only be as good as the surface you are going to paint. You need to have a secure, strong bond for the paint to adhere properly. How can you determine whether you can go ahead with painting over polyurethane? Below are three situations to consider.
- A piece of furniture that has been properly looked after with no damage like deep scratches, gouges, or peeling paint. In this situation, the process will be fairly straightforward. Wash the surface, wipe it clean, scuff it slightly if it is glossy, and then paint.
- If the piece of furniture has been neglected and has scratches and gouge marks on the polyurethane finish, it needs more attention. Sand the surface properly, fill the gouges and scratches with wood filler, follow the cleaning process shown above, and then paint.
- When a piece of furniture has been badly damaged and the polyurethane coating is peeling off, revealing the wood below, you must not paint over this surface. You need to use some paint stripper and remove the entire polyurethane coating, and then start from scratch.
How to Paint Over Polyurethane
A polyurethane coating is a durable and strong surface finish that can protect your wood, which also means that you cannot just paint over it, as your paint will not adhere properly. However, with the correct materials and a little bit of hard work, you will be able to paint over your polyurethane finish.
Polyurethane can be either oil- or water-based, so you will have to consider what type of paint you are going to use over your finish; we will be covering this aspect a little later in our article. However, the process we are about to guide you through should be followed regardless of whether it is a water- or oil-based polyurethane coating.
The most important factor to consider is the preparation of the surface; this does not mean you have the remove all of the polyurethane finish. But preparing the surface correctly will give you the rough texture that is needed for your paint to adhere, thus giving you a long-lasting finish. So, we invite you to join us on this journey of painting over polyurethane.
Tools and Supplies Needed:
- Clean cloths that are lint-free
- Wood filler
- Safety goggles
- Face mask or respirator mask
- Rubber gloves
- Protective clothing
- Various grades of sandpaper
- Sanding machine (if necessary)
- Mineral spirits
- Oil-based primer
- Oil-based paint or acrylic urethane paint
- Deglosser or Liquid sandpaper (optional)
Preparing the Wood Surface
The very first thing you need to do is to make sure all the dust, grime, grease, mildew, and mold have been removed. For this, you can use Trisodium Phosphate (TSP), a very strong cleaning solution. However, before you start, you need to wear rubber gloves, safety goggles, a face mask, and protective clothing, as it is very toxic and not environmentally friendly. Be sure to open some windows so that the area you are working in is properly ventilated.
Take a bucket and add one gallon of water, then add a quarter cup of TSP and mix well. Next, take a hand sponge with an abrasive side and dip it into the mixture, wring out the excess, and then start wiping the polyurethane surface in circular motions. Do this until all the dirt and grime are gone.
If you still find some areas with stubborn stains, sprinkle some of the mixture over the affected area and scrub with a bristle scrubbing brush, using circular movements.
If you are in any way intimidated by the use of TSP, then there are other alternatives that you can use. For a milder cleaning solution, add one gallon of water to a bucket, and then add one tablespoon of dishwashing liquid and stir well. You may also try mineral spirits, but you must ensure that the surface is completely clean afterward.
Allow about 15 minutes for the wood surface to dry, and use a clean, dry cloth to wipe the surface. Now is the time (if necessary) to take a putty knife and use wood filler to fill all the cracks, holes, chips, and to fix any other surface imperfections. When using wood putty, try to apply it evenly with your wood, and allow the wood putty to dry completely.
Sanding the Wood Surface
There are a lot of people that think it is unnecessary to sand your polyurethane before you paint it, mainly because it is a very messy job. However, sanding is extremely important, as this will give you an even surface and allow your paint to stick properly. Sanding is recommended for all surface preparations.
Remember to wear a face mask and safety goggles before you start sanding to protect your lungs, as the sanding creates a lot of dust. If you have a very smooth surface, you may want to start with 60- or 80-grit sandpaper. You can use 120- to 220-grit to remove the yellow stain of the polyurethane. You need to be sure that the wood surface is rough enough to hold the paint that you are going to apply later.
You can use contour sanding grips for any difficult, curved pieces, and for concave curves or holes, you can use a drum sander attachment or a Dremel, which can be attached to your drilling machine. When sanding, use circular movements until you have covered the entire wood surface. Then, use a vacuum cleaner to remove all the dust and wipe the surface with a clean cloth dipped in some mineral spirits.-
Are there other options apart from sanding your polyurethane surface? Yes, you can use a deglosser, otherwise referred to as liquid sandpaper. This is ideal to use if you have a very large area to cover or where there is fine, detailed work that could be difficult to sand by hand. However, you need to take care when working with it, as it is a very powerful chemical that etches the surface of the polyurethane, allowing the paint to stick to it. This means that you need to wear all the necessary protective equipment required for the use of dangerous chemicals.
We recommend that before you use it, try it out on a small section of your project to ensure that it will not damage your wood. To apply, all you need to do is saturate a clean lint-free cloth in the chemical, wipe it over the whole surface, and allow it to dry – you will then be ready to apply your paint.
Applying the Primer
Can you follow the process of painting over clear coat directly without giving it a primer coat first? Doing this can pose two major problems: First, the paint will not have a surface to grip onto properly, which could cause it to peel off. Secondly, without an oil-based primer, the tannins in the resin of the polyurethane may bleed through, leaving you with a yellow or orange appearance. These problems can be avoided by applying the correct primer.
Applying a primer to your polyurethane finish is essential, so what type of primer is the best to use? An oil-based primer is the only type of primer that is compatible with your polyurethane finish. You may now wonder if any oil-based primer is the best to use. Well, the best primer that will give you the best result is a high-quality bonding primer, as it not only ensures your paint will stick but also requires fewer coats for full coverage.
To apply the primer, you can use a natural-bristled paintbrush for small areas or a foam roller for larger areas. Many jobs can also use both of these options. Using smooth up-and-down movements, cover the entire surface with a thin layer and allow it to dry completely. Check the manufacturer’s instructions for the correct drying time. If you are applying the primer to a dark wood or to polyurethane that is dark-colored, it may require a second coat after the first coat has properly dried.
After you have applied the primer and it is completely dry, you need to gently sand the surface. Try not to sand it so much that you go right through your primer coating. The idea is to sand the brush strokes and get the surface flat and even. If you fail to do this step, it may result in freckled and discolored stains appearing after you have applied the final topcoat of paint.
Applying the Final Topcoat of Paint
Is it tricky to paint over polyurethane? The only tricky part is getting the paint to stick properly to the polyurethane surface. Polyurethane consists of oil solvents, and painting directly over this type of surface with water-based paint can lead to problems if you did not cover it with primer properly.
Also, bear in mind that polyurethane comes in semi-gloss and gloss finishes, and this can pose a problem for the new paint. However, there is no problem in painting over a polyurethane finish with water-based paint if you follow the processes listed above, which are:
- Preparing the wood surface
- Sanding the surface
- Applying a primer
If you follow these steps correctly, you should have no problem with water-based paint adhering to the polyurethane surface. The use of water-based paint is a good choice, as it has no harmful odors and it can dry a lot faster than oil-based paint.
However, many recommend that you paint over a polyurethane surface with oil-based paint, as it will provide you with a far superior and more durable finish. While you can paint over your polyurethane surface directly with oil-based paints, if you want to achieve the best results, all the steps recommended for water-based painting should also be adhered to when painting with oil-based paints.
You can apply the paint with a roller if it is a large area, or with a brush if the area is smaller. Try to apply a thin layer of paint using vertical, even strokes. Try to paint in smaller segments and apply it until the paint is over the entire surface.
We would like to mention here that you can also paint over your polyurethane using a spray gun, which will be able to give you a more precise thickness over the surface area.
Wait for about an hour and feel if the paint is dry to the touch – if it is dry, you can then proceed with a second coat. If at this stage the primer is still visible, apply a third coat and allow it to dry for around 72 hours before you use the surface.
What Types of Paint Can You Paint Over Polyurethane?
The truth of the matter is that you can use any type of paint for painting over polyurethane if you have treated and prepared the surface correctly. This means that no paint you use will be able to stick properly to your polyurethane surface with improper preparation – it will always lead to the paint peeling or chipping. To simplify this matter further, we have drawn up a small table to show you what paints can be used to paint over polyurethane.
|Paint||Can Be Used to Paint Over Polyurethane||Remarks|
|Oil-based paint||✔||Can be painted directly over polyurethane, but sanding the surface first is recommended|
|Water-based paint||✔||Can be painted over polyurethane, but it is recommended that you prepare, sand, and prime the surface first|
|Latex-based paint||✔||Can be painted over polyurethane, but it is is recommended that you prepare, sand, and prime the surface first|
|Chalk paint||✔||Can be painted directly over polyurethane, but sanding the surface first is recommended|
Some Useful Precautionary Tips When Painting Over Polyurethane
Remember that the paints and primers you will use all contain harmful and dangerous chemicals, so before you start painting over polyurethane, you need to take some precautionary measures to protect yourself.
- Only work in a well-ventilated space, preferably outside. If you do need to work indoors, ensure that you open as many windows as possible to give you proper air circulation.
- Be sure to use protective equipment such as protective goggles, protective eyewear, and rubber gloves, and as well as a respirator to protect your lungs.
- Try not to work in extreme weather conditions, as rainy days, for example, may affect the curing process. Try to work on sunny days, as the best results for painting over polyurethane can be achieved at 70 degrees Fahrenheit (21 degrees Celsius) or more.
- As many of the paints contain flammable and combustible materials, do not smoke near your working area and keep flames and fires away.
- Make sure you dispose of your excess materials correctly. Do not throw the solvents or paints down the drain, and do not just put your soaked cloths in the garbage bin – these items must be disposed of safely.
Frequently Asked Questions
Is Painting Over Polyurethane Possible Without Sanding?
Yes, you can avoid sanding if you use oil-based paint, but it is always recommended to first sand the surface and then apply your paint, as it helps to improve the finish.
Can You Apply Primer Over Polyurethane?
Yes, this is important for a more durable paint finish over polyurethane. Just as sanding is recommended, applying a primer before you paint is extremely useful in increasing the paint’s adherence to the polyurethane, especially when using water-based paint.
What Primer Can I Use to Paint Over Water-Based Polyurethane?
Whether you are going to paint over oil-based or water-based polyurethane, you need to use a good-quality oil-based primer; a bonding primer is recommended.
What Does a Deglosser Do?
A deglosser, also referred to as liquid sandpaper, can be used instead of sanding, and is especially useful for if you have a large area to paint or fine, detailed work. First, try it out on a small section to see if it will damage your wood or not before using it.
Do I Need to Sand After Using a Deglosser?
No, you do not have to sand after you use a deglosser – you must not even wipe it off. Apply the deglosser, wait for it to dry, and then you are ready to apply your paint.
Is Painting Over Varnished Wood Possible?
As polyurethane can be regarded as a type of varnish, then painting over varnished wood is also possible – simply follow the same processes as for polyurethane.
Will Paint Stick to Polyurethane?
If you follow all the basic processes shown above, like preparing the surface, sanding, and applying the primer, then any paint you use will stick to the polyurethane.