You opted to keep that natural look for your woodworking project, floors, or piece of furniture. You wisely used polyurethane to give long-lasting protection to the wood from elements and aging. If you are considering adding stain to your project that is already coated in polyurethane, I have steps to help you.
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Test the Stain Over Polyurethane
The goal of stain is to alter the color of wood and make wood grain stand out. If there is quality polyurethane already on your project, I recommend trying to find a remnant of your work. Testing on an extra piece will give you the opportunity to see probable outcomes on a small scale that won’t damage the item on which you are working.
If the test piece is already coated in polyurethane, wonderful! Otherwise, apply polyurethane to the extra piece of wood. Replicate conditions as similar as possible to your original project.
Variables to replicate include:
- Brand of polyurethane (Minwax, etc)
- Temperature
- Humidity
- Curing time
Tip: Make sure to follow manufacturer instructions for cure time. Water-based and oil-based polyurethanes cure at differing rates.
Apply Traditional Stain to Polyurethane
After your polyurethane has cured, apply your wood stain.
- Apply your stain using a foam brush, bristle brush, or clean cloth. Applying pressure as you stain forces stain deeper into the wood’s pores and will likely achieve a longer-lasting finish. This is most easily accomplished by applying stain with a clean rag.
- Use the edge of your paint brush bristles or a toothpick to pop bubbles in the stain.
- The longer stain remains on the wood, the darker the wood becomes. Determine how long the stain should remain on the wood, then set a timer.
- Wipe away excess stain when your time is up. Do not let the excess stain dry on your wood.
Visually inspect your remnant. If you have followed the steps outlined above, it is likely that your project will exhibit the same coloration and stain absorption as the remnant. You can confidently stain your polyurethaned wood if you are content with the outcome.
If you are dissatisfied, I have more options for you to consider.
Use Gel Stain Over Polyurethane
Polyurethane fills the pores that stain needs to work effectively. Using a gel stain may be the most effective, straightforward way to stain over polyurethaned wood. Gel stains create a durable coating on top of the surface of the wood.

To apply gel stains:
- Wipe raw lumber of all dirt. Degrease, wipe, and lightly sand finished lumber.
- Apply gel stain uniformly with a foam brush.
- Remove excess gel stain with a rag.
- Allow gel stain cure, usually 24 hours.
- Apply additional coats as necessary. Smooth, glossy finishes usually require several coats.
Remove Polyurethane Then Apply Stain
If you want to use traditional stain, opening the pores of your project will help it to more easily and uniformly accept stain. Removing or abrading polyurethane in the area to be stained will be necessary for most methods.
Sand the Wood
Perhaps the simplest way to apply stain to polyurethaned wood is to sand away the polyurethane. Polyurethane fills the pores of wood. Sanding through the coats of polyurethane will expose unfilled pores that are ready to accept stain.
It may be the case that you have accidentally spilled or prematurely brushed polyurethane on your project. If you are able, quickly wipe away the polyurethane with a clean rag to limit the sanding required to open the pores.
Hand Sanding
Hand sanding polyurethane will give you the most control in opening up wood pores.
- Consider the weight and size of your project. If needed, secure your project to a work surface using clamps.
- Using medium grit sandpaper, sand in long strokes following the grain of the wood. Take care not to sand across the grain as this will likely result in waves within the wood. Use your remnant piece to practice if possible.
- After the polyurethane is removed, switch to a fine grit sandpaper (#220) for a smooth finish.
Random Orbital Sanding
If you have a random orbital sander, you can also use it to sand your piece more quickly and efficiently.
- Make sure your piece of wood is clean and secured.
- Using a medium grit sandpaper (#120), work your way slowly across your project. Try not to move your sander faster than 1 inch per second. Allow the sander to do the work. Do not firmly press your sander into the wood.
- If multiple passes are required to sand the entire surface, significantly overlap each pass. You should overlap between 1/3 to 1/2 of your sanding pad with previous passes.
- When sanding is complete with your initial grit, wipe the surface clean with a damp cloth. Wearing gloves and goggles, wiping with a cloth dampened with mineral spirits is great for removing dust.
- Allow the surface to dry completely.
- Switch to fine grit (#220). Repeat steps 2-5
- Hand sand the surface with #220 grit sandpaper.

Now that the polyurethane is removed, staining your piece evenly should be possible. If the project you are working on will later require gluing and screwing pieces together, consider leaving contact areas unstained. Areas without polyurethane and wood stain will accept glue more easily.
Hand Plane the Wood
The best hand planers remove thin layers of wood. The amount of wood that can be removed with each pass of the hand planer can be adjusted but will always remove relatively thin layers.
- Secure your project using clamps if necessary.
- Paying attention to the grain. Plane with the grain going up and away from you.
- Use even downward and forward pressure on the planer. Each pass should travel the entire length of your board.
- Repeat as necessary until all polyurethane is gone.
With the polyurethane gone, your wood should be able to accept stain.
Understanding Stain and Polyurethane
Wood stains darken wood and can highlight beautiful wood grain patterns. Color compounds within the stain penetrate into the pores of wood. The longer stain is allowed to rest on the surface of an unfinished piece of lumber, the deeper the stain will penetrate. Aside from aesthetic value, stained wood has some water-repellent qualities and is more resistant to discoloration from sunlight.
Polyurethane is a must on most carpentry projects. When correctly applied, polyurethane provides solid protection from water, sun, bugs, even dents and dings. It prevents most things, including wood stain, from entering wood pores by filling and sealing pores in wood.
Wood stain does not seal wood like polyurethane. If you are working on a project beginning with raw lumber, in nearly every case you will want to apply stain first, then apply polyurethane to your dried, stained wood. I have techniques that allow you to apply stain to wood coated in polyurethane.
Impact of Polyurethane and Stain on Wood Grain
Wood grain is the waves of lighter and darker looping sections within a piece of wood. Wood grain present in a piece of lumber is a combination of the tree’s growth rings and method used to saw your lumber.
Different types of wood vary in density. Lighter areas in the wood represent rapid growth usually associated with spring or the early growing seasons. Quick growth creates large, straw-like cells that can deeply and more quickly absorb stain or polyurethane.
Dark, narrow bands within the wood represent the end of growing seasons or a particularly harsh environs. These darker, denser cells accept stain and polyurethane slowly. Varying penetration rates of stain and polyurethane rates highlight the wood grain.
Conclusion
To stain over polyurethane likely requires gel stain or altering the project’s surface. In most instances, removing the polyurethane is necessary to apply stain to wood. Gel stain allows you to easily apply a stain to your polyurethaned wood.