How To Remove Polyurethane From Wood (Step-by-Step Guide)
Polyurethane, lacquer, varnish, and other clear coats are applied to the surface of wood in order to protect and extend its life. This will stop any scratches, scuff marks, gouges, or damage from reaching the wood and instead, only affect the top layer. This top layer can be removed and reapplied when needed, much like a screen protector for your wood items.
The most common ways to remove polyurethane are sanding and chemical stripping. Sanding does not involve harsh chemicals, but it is messier. Chemical stripping takes the hard work out of the project, but you will need good ventilation.
Any of these processes will remove the finish from the wood, allowing you to refinish it the way that you would like. They involve different methods, tools, and materials, so read below to find out which will work best for you.
What is Polyurethane?
Polyurethane is a liquid that dries into a plastic-like substance. It is available in water and oil base and comes in many different varieties, from satin to shiny. Either of the common varieties that you use, water-based or oil-based, can be applied to latex and acrylic paint.
If using oil-based, you will notice a yellow hue, which is what helps the wood to glow, but might make white paint look off-color. In this case, you would want to go with a water-based polyurethane.
One of the more popular types is water-based, as it has a very low odor and low toxicity. Similar to shellac, it won’t hold up well against heat or chemicals.
Water-based polyurethane is not a good option for places where you will be resting pans or other hot objects. It is a great choice however for bookcases, desks, dressers, chairs, and the like. It also goes on clear when applied, which is different from oil-based which will add a little bit of color to the wood.
Polyurethane that is oil-based is more durable than water-based and more often used in the kitchen. It helps bring out the richness of wood and makes the different color variations pop. Because of its strong smell, you should use a mask when applying and only do so in a well-ventilated area.
This type of polyurethane can be applied using a natural-bristle brush or a rag, whichever makes the most sense for application. It takes longer to dry and cure than water-based, though the wait is usually worth it if you can properly ventilate the area.
Water-Based Oil-Modified Polyurethane
There is also water-based oil-modified polyurethane, which is a new product to the market. When using this type, you get the durability of the oil base with the ease of cleanup of the water base.
Before Removing Polyurethane
When removing polyurethane, do so in a well-ventilated area. If you can work outside that will be your best option, if not, try to create cross ventilation in the area you are working. Open windows on opposite walls, this will allow a breeze to push the vapors out of the room. You should also protect the floor where you are working by laying down a drop cloth.
If using chemicals to remove polyurethane, wear the appropriate safety gear. A mask or ventilator to protect your lungs, gloves to protect your hands, and if sanding, eye protection should be used.
Sanding to Get Rid of Polyurethane
Sanding is one of the most labor-intensive ways to remove polyurethane, but it does not involve any harsh chemicals. Sanding can also be used to remove nearly any other wood finish. This makes it a great choice if you aren’t totally sure that it’s polyurethane on top of the wood.
Tools You Will Need for Sanding:
- 150-grit and 220-grit sandpaper
- Orbital Sander
- Sanding Block
- Safety Protection (Gloves, Mask, Eye Protection)
Step 1: Set-up Your Workspace
Lay down a drop cloth under your workspace, this will help keep the mess to a minimum. Wear a respirator or mask so you do not breathe in the wood dust as you are sanding and use eye protection. You will also want to have a vacuum handy for cleaning up afterward.
Step 2: Sanding the Wood
Attach a piece of 150-grit sandpaper to your orbital sander. This is what you will use to remove the polyurethane from the wood.
Starting from one end of your piece of wood, lightly sand while following the wood grain. Move the sander in small concentric circles to keep things even. Make sure you are not pushing down on the sander too hard, as this will cause the motor to work harder than it needs to. Keep an even pressure as you go and cover the entire length before starting over again.
Once all the polyurethane has been removed, use the 220-grit sandpaper. This will smooth down the wood and make it soft and blemish-free.
Using Solvents to Remove Polyurethane
Tools You Will Need When Using Solvents:
- Chemical Paint and Varnish Stripper
- Paint Brush
- Paint Scraper
- Orbital Sander
- 150-grit and 220-grit Sandpaper
- Rags or Clothes
- Safety Goggles, Gloves, Mask
- Bucket and water
Step 1: Setup and Clean the Surface
Wipe down the surface of the wood that you will be removing the polyurethane from. Let it dry completely before moving onto the next step. While it is drying, set up your workspace. Lay down a drop cloth to catch any spills and set up fans to help with the fumes.
Open all the windows to the room you are working in and if possible, it’s best to work outside. Make sure that you are able to get fresh air into the room, as the fumes are very strong.
Step 2: Apply the Chemical Solvent
Apply the polyurethane stripping chemical to the surface of your wood using the paintbrush. Use a liberal amount as you will want to apply enough that it can sit for 20 minutes without drying out. Brush in the same direction as the wood grain and avoid using a back and forth motion.
Step 3: Breaking Down the Polyurethane
Allow the chemical remover to sit for at least 20 minutes. This gives it ample time to work its way into the polyurethane and start breaking it down. Each brand of chemical solvent will have its own recommended time frame, so check the instructions to get the best results.
Step 4: Scraping Off the Polyurethane
Scrape the surface of your wood with the paint scraper. You will be taking off the chemical remover as well as the softened polyurethane. Afterward, wipe the wood clean with a rag. You will want to do this after every application of polyurethane remover. Continue to apply the chemical removal solvent and repeat the steps until you have removed all of the polyurethane.
Once finished, run the sander over the surface using the 150-grit sandpaper. This will make sure to get everything that might have been left behind, as well as give you a fresh layer to work with. Afterward, switch to the 220-grit sandpaper. This will smooth down the wood and make it soft and blemish-free.
Clean the surface of the wood with water and rag and let it dry out completely before adding a new layer of sealant, varnish, or paint.
Is it Better to Spray on or Brush on Polyurethane?
Some polyurethane comes in an aerosol spray can and is good for surfaces that are rounded. For flat surfaces, you are better off using the brush technique. This will help build up a durable layer that is even and smooth.
Does Vinegar Remove Polyurethane?
Vinegar is will remove polyurethane, though not as well as a chemical remover. Because it is more liquid you won’t be able to layer it on. It will also take more effort when scraping, as it won’t break it down as quickly or evenly. It is a safer choice if you are worried about fumes and chemicals, but it is not as effective.
Why is My Polyurethane Bumpy?
Usually, this is a result of shaking the can and allowing air bubbles into the substance, or not using the paintbrush correctly. When you wipe the brush against the side of the can before applying the polyurethane, you can introduce air bubbles into it. It is better to get a good amount on the brush by dipping it straight in, then applying directly.When applying polyurethane, run the brush lightly over the coat you just applied, and this will help flatten any bubbles. If you notice bubbles in your dried polyurethane, you unfortunately only have two options: Live with them or sand them out and add another layer.
Sean Jarvis is an interior decorator, writer, and expert handyman. Well versed in everything home improvement, he is a savant at manipulating words and spaces and upgrading everything around him. Sean specializes in writing concise guides about appliance repair and installation, home and lifestyle, and other residential projects.
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