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There are three different methods for removing varnish from wood: using sandpaper, a heat gun, or varnish stripper. It will also cover how to tell if wood was finished with lacquer, varnish, or shellac.
Removing Varnish From Wood With Varnish Stripper
Using varnish stripper is the most effective method for taking varnish off of wood. While it does involve chemicals, it is the fastest and most precise method for getting all of the varnish off.
Don’t confuse this product with paint thinner – varnish stripper is much harsher. OSHA requires employees exposed to varnish stripper to be issued properly fitting respirator masks and gloves, make sure you have the same protection in your workspace.
- Confirm the finish is varnish. Use the section below to determine if you’re stripping varnish polyurethane, lacquer, or shellac. You may be able to use a less harsh chemical, such as a solvent, instead of a stripper. Denatured alcohol is great for removing lacquer, while polyurethane responds well to acetone. Removing shellac from wood will involve chemicals.
- Make sure you need to remove the varnish. If you’re planning to paint the wood and the varnish is not cracked or peeling, you don’t need to remove it. Rough up the surface with 180-grit sandpaper to provide a surface that will accept primer.
- Set up a suitable workplace. Work outside or open all the windows and doors. Run a fan. Varnish strippers contain an active ingredient that dissolves the bonds between wood and varnish. The most common active ingredient is methylene chloride. Avoid contact with methylene chloride varnish strippers, as they have been linked to a number of health concerns.
- Protect yourself. Use a respirator mask to protect your airways. Use nitrile gloves to cover your hands. If your stripper contains methyl ethyl ketone, choose latex gloves for better protection. Change gloves frequently to avoid degradation of the material.
- Apply the stripper. Similar to how you apply varnish, use a brush to apply an even coat of varnish stripper over the entire project. Wait for the stripper to work. The label on the product should tell you how long you need to wait.
- Scrape the varnish. Use a plastic scraper to peel off the sticky, gloppy varnish. Be careful not to scratch or gouge softer woods. You can use 0000 steel wool to clean difficult areas.
Removing Varnish From Wood With Sandpaper
While other methods rely on changing the structure of the varnish by dissolving it with chemical or heat, sanding simply blasts it away. This method is the most physically intensive and takes the longest, but does not require any harsh chemicals.
- Choose your tool. Using a random orbital sander is the fastest way to remove varnish from wood. Simply plug it in, turn it on, and move it back and forth across flat open areas to remove varnish. If you have the patience, you can also sand varnish using a sanding block.
- Sand the wood. Start with 150-grit sanding paper to break through the top layer of varnish and scuff the entire surface. Use 220-grit sandpaper to finish the job. Don’t use a power sander over carved areas, as it will quickly sand away definition. To maintain crisp details, consider using a chemical stripper.
- Protect yourself. Always use a GFCI rated outlet when working with power tools. Remove any dangling jewelry. Cover your mouth and nose with a dust mask to prevent inhalation of sawdust.
- Clean up. Use a handheld vacuum or shop vac to suck up the debris left over from sanding. Wipe the surface of the wood with a tack cloth to remove dust.
Removing Varnish From Wood With a Heat Gun
If you don’t have access to a well-ventilated area or a random orbital sander, don’t fret. You can still remove varnish from wood, using a hiqh quality heat gun.
- Safety first. Plug the heat gun into a GFCI-rated outlet. Wear gloves and thick sleeves to protect your skin. Heat guns operate at temperatures that can top 1000 degrees Fahrenheit, so serious burns can occur if they are mishandled.
- Melt the varnish. Point a heat gun at the varnished surface. Select a medium temperature setting and turn the gun on. In a few minutes, the varnish should start to bubble. A few more, and it will begin to drip.
- Adjust the heat. If varnish does not bubble, or bubbles without dripping, the air from the heat gun isn’t hot enough. Try again with a high heat setting.
- Scrape the varnish. When the varnish is liquid and beginning to run, use a putty knife to scrape off the varnish. Be careful not to scrape the wood underneath. Work in small sections at a time.
Is it Varnish, Lacquer or Shellac?
When dried, it can be difficult for the unpracticed eye to distinguish between varnish and transparent, hard, glossy finishes such as lacquer or polyurethane or shellac. Tints added during the production process can further muddy the waters. Varnish destined for removal probably has some defects, including cracking, blushing, or peeling.
Learn about the differences in varnish and lacquer in our detailed guide.
So how do you know if you’re dealing with varnish or something else?
How to Determine Wood Finish
You can quickly and easily figure out what kind of finish was previously applied to wood using cotton swabs, acetone, and denatured alcohol.
- Grab some cotton swabs and some acetone (the kind used in some nail polish remover is fine, as long as it says acetone on the bottle). Wet the tip of the swab with acetone and carefully rub it against an inconspicuous area of the wood.
- If the acetone beads on top of the surface, it was finished with polyurethane. If the finish completely dissolves upon contact with acetone, then it was finished with lacquer.
- Both shellac and varnish will become sticky when confronted with acetone. To make the final evaluation about what kind of finish you’re dealing with, you need to conduct another test. Wet the tip of a clean cotton swab with denatured alcohol.
- Apply the alcohol to a second inconspicuous spot on your workpiece and watch it for a few minutes. If the finish immediately begins to dissolve into a liquid, that’s shellac. If it’s varnish, the alcohol takes longer to work, so it will take a few minutes before you see the dissolution happen.
Varnish can be removed from wood using varnish stripper, sandpaper, or a heat gun. Observe safety protocols to avoid accidental injury. Wear personal protective equipment and work in a well-ventilated space.