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Polyurethane is a synthetic resin used in a diverse range of items, from household items to industrial products. Water-based polyeutherane is especially popular used as a finish over wood, acrylic, or latex surfaces. Painting over our furniture is one of the ways we can preserve and beautify pieces, but can we paint over something coated with polyeutherane even without sanding? We've researched this to get the answer for you.
Painting over polyurethane will only end with peeling, so you will need to sand and prime it first. Failing to prep your furniture for painting will result in peeling that a single fingernail scratch can cause, if not natural circumstances. After sanding, you should also lather a good quality primer over the surface to protect the color and to ensure a smooth painting process.
There is still a lot to learn and unpack about the process of painting furniture. Trial and error can only get you so far, so we have researched on ways you can paint over polyurethane more effectively and efficiently. Stay with us to learn more!
What is polyurethane?
Polyurethane is a type of varnish used in finishing furniture, woodwork, and floors. It is a protective coating that many people use because it is resistant to water, mildew, and fungus, as well as scratches.
Polyurethane varnishes can be oil-based and water-based, although most people use water-based varnishes because it is more cost-efficient and environmentally-friendly.
This type of varnish creates a hard, shell-like finish and leaves a slightly yellow sheen. It is mostly applied to outdoor furniture and woodwork subject to regular use since it makes the paint durable.
These varnishes are fairly easy to apply and have a more flexible finish. It requires a few more coats to achieve a durable and shell-like finish, which makes it more suitable for indoor furniture.
What happens if you paint over polyurethane straight away?
Paint will most likely slide right off the surface. This is because polyurethane is made of complex alcohol, along with a petroleum byproduct which creates a resilient long-chain molecule that is difficult to penetrate.
Paint needs to bond to porous surfaces to create adhesion, which is why you need to physically sand the surface or use chemical strippers first to weaken the chemical bonds and make paint stick.
Orange tint over the color
When you paint directly over polyeutherane, resins in the wood can rise and blend with the paint which can produce an orange or yellow tint on the furniture. Sanding and applying a thick layer of primer can help you avoid this problem.
How to remove polyurethane with Sanding
Upcycling your furniture should begin with removing the polyeutherane coating. Sanding is one of the basic ways to do this. Make sure you are in a ventilated area and wearing protective gear to eliminate health risks.
What you’ll need
- Heavy and light-grit sandpaper
- Orbital sander
- Sanding block
- Old sheets
What to do
- Place old newspapers or plastic sheets to cover the surrounding area of the furniture.
- Wear your protective equipment to prevent any accident.
- Attach a 150-grit sander onto the orbital sander.
- Sand the flat surface with the orbital sander.
- Sand the curve-shaped areas with a sanding block or sandpaper.
How to remove polyurethane using chemical strippers
Chemical strippers are an easier—albeit risker—way to remove the polyeutherane coating. Make sure to be in a ventilated area while wearing protective equipment to protect yourself from inhaling or being in contact with harsh elements.
What you’ll need
- Paint brush
- Chemical stripper
- Paint stripper
- Rags or paper sheets
- Eye googles and gloves
- Floor Scraper
What to do
- Cover the surrounding area with paper sheets to protect it from stains.
- Wear protective equipment since you will be using harsh chemicals.
- Clean the surface and let dry
- Thickly lather the area with paint remover using a paintbrush.
- Apply the chemical remover on the surface. Let it sit for 20 minutes, but it is best to follow the brand’s user instructions.
- Scrape off the softened polyeutherane and wipe with rags.
- Repeat until the surface is free of polyurethane.
Can you use a heat-gun to remove polyurethane?
Sanding takes a lot of time and labor, while chemical strippers can be highly toxic. If you want other options other than sanding to remove polyeutherane, heat guns are a quick and non-toxic way you can do this. It may take a bit of practice, but it can be done by the average person.
What you’ll need
- Drop cloth
- Protective glasses
- Respirator mask
- Paint scraper
- Heat gun
What to do
- Wash the surface, then promptly dry.
- Cover the polyeutherane-coated area with a drop cloth.
- Set the heat gun’s temperature to medium.
- Slowly move along the area, two inches above the surface.
- Carefully scrape when polyeutherane starts bubbling up.
- Repeat the process until there no more polyeutherane is stuck.
- Sand the area to remove remaining pieces of polyeutherane.
Painting over polyurethane the right way
Sand the surface
Sanding can take several passes with either light or heavy-grit sandpapers. Heavy grit sandpapers can penetrate the polyeutherane surface, while light-grit sandpapers can smoothen the surface and prevent major scratches on your wood. A palm sander can reduce the labor-intensive process, but you might still need to manually scratch over table legs and spindles using a sandpaper.
Optional: applying a coat of deglosser
This type of liquid sandpaper can work in the same way without the physical exertion, however, it is a very strong type of chemical that would need to be handled with protective equipment. There is also a risk of lung damage and nausea, so proceed with extreme caution should you choose to apply this instead.
Also, note that some furniture may not be compatible with this harsh chemical, so you need to test it on a small portion of the surface first.
Lather a coat of primer
A bonding primer will serve both as an adhesive and a barrier for your paint. It will prevent resin tints from bleeding through the paint, making the color consistent all throughout. Take note that it is important to apply it with thick and even strokes.
Painting over the surface
Once you have finished sanding and priming, you may assume that painting should take the shortest time. However, this can take you a little over three days.
- Free the surface of any dust or dirt.
- Apply the first topcoat of paint.
- Wait for the paint to cure and dry. This can take around 72 hours.
- Add a second layer of paint or decorate.Wait again for around 72 hours.
- Make sure everything is dry and cured.
- You may now place objects on top of your furniture.
What paint works over polyurethane?
Identifying the paint that would best suit your furniture is important to making it last long. Here are some effective and easily-manageable paints you can coat over a sanded and primed surface.
Chalk paint is famous for its unique qualities, particularly its ability to stick through any surface without much preparation. It has a matte finish that can beautify any surface and give it a rustic appeal.
However, it is still important to sand the furniture if it has a polyurethane coating since chalk paint can easily peel off without any protective coating.
Acrylic Latex Paint
Acrylic Latex is a water-based paint that is easy to use and very forgiving with mistakes since it cleans up well with just soap and water. The synthetic polymers will easily stick to a sanded and primed surface and can dry within a few hours.
Water-based paint is much more cost-effective than purely oil-based paints. It also holds up well on wood, stone, or wicker since these are porous surfaces in which adhesion is ideal. Just don’t forget to sand the surface and apply a primer to avoid peeling.
Enamel paints give your surface a durable and glossy finish. It is a practical choice for furnitures that are subject to regular wear and tear, since the finish makes the paint last longer. It is ideal to use fine-grit sandpaper to prep the surface to get rid of any ridges and to enable stable adhesion.
Acrylic enamel is often used for objects that are often placed outdoors, such as house exteriors and cars. It is also suitable for unprepared wood, but only if it is uncoated. If it has been coated with polyurethane, sanding and priming must be done first.
Painting over polyurethane is possible, but it can be peeled and ruin the surface without proper sanding and priming. If you want to upcycle your furniture or repaint your interior, you want to remove the polyurethane coating first to make your paint stick and make it last a long time.