Polyurethane has a smooth clear coat finish. But, sometimes, the finish of polyurethane develops scratches. So, how to fix or remove these scratches?
To fix light polyurethane scratches, wipe the scratched spot with mineral spirits and buff it with wax. To fix deep scratches, sand the surface and fill the scratch with a scratch-repair polyurethane pen.
If the scratch spot looks darker than the surface, it has affected the wood. In this case, you must remove polyurethane, apply wood filler, and re-seal the wood.
Why Does This Happen?
The main reason for polyurethane scratches is wear and tear. Over time, a polyurethane finish will develop scratch marks due to friction, dropped items, pencil marks, etc.
Here are some other reasons why this happens:
- Pet Claw Marks – If you have a pet cat or dog, your pet’s claws can scratch your polyurethane finish. This isn’t limited to floor surfaces, because your pet can pounce on a finished desk and scratch it. The best way to avoid this is to trim your pet’s claws frequently.
- Toys – Dragging toys across the floor or table can cause scratches on the finish. Luckily, these are light scratches and can be fixed easily.
- Cleaning Products – If you clean a polyurethane finish with the wrong cleaning products, it can cause scratches on the finish. Some cleaning products can dissolve and soften the polyurethane finish. When this happens, the finish will develop scratches from the lightest touches.
- Wrong Sandpaper – You must sand between coats of polyurethane with fine-grit sandpaper. But, if you use medium or coarse-grit sandpaper, the finish will reveal scratches. If you use the wrong sandpaper too much, you can ruin or remove the entire finish.
- Filthy Surface – If the floor is filthy or filled with sand grains, you can scar the finish. While walking, you can push and drag the sand grains into the polyurethane finish and create a rough finish.
- Wrong Cleaning Attachment – You can scar a polyurethane finish while cleaning the floor with abrasive or spiky cleaners.
Can You Touch Up Polyurethane?
You can only touch up a polyurethane finish if it has a coating scar. If the mark has only affected the coating and not the surface underneath, you can touch up the finish with an extra coating or a scratch-repair pen.
You can touch up a surface by applying a fresh coat of polyurethane over the existing finish. The new coat will fill and cover the affected spots. However, you must sand the existing coating before adding the new coat. Sanding will remove grime and bumps on the finish that can prevent the new coat from sticking.
You can also touch up polyurethane using a scratch-fix PU pen or a scratch-repair marker. These markers are filled with a mix that fits all types of clear coats. You just need to pick the pen with the same color or shade as your existing finish.
However, if the scar is deep and has penetrated the wood, you can’t touch up polyurethane because the scar is too deep for the touch-up to cover or fix. In this case, you must remove the entire finish, apply wood filler, and re-seal the wood.
How To Fix Scratches On Polyurethane Finish?
Before you can fix scratches in polyurethane finish, you must know their type:
- If the abraded spot looks darker than the surrounding finish — it’s a deep mark, and you must strip and re-seal the wood to fix it.
- If the scratch spot has the same color as the finish — it’s a surface scratch and can be touched up.
- Is the wood stain underneath affected? – It’s a film scratch, and sanding is required.
- Wipe the abraded spot with mineral spirits — if it comes off, it was just a stain.
1. Use a Scratch-fix Pen
To fix a light-abraded spot on a polyurethane finish, use a polyurethane marker pen. The marker pen is filled with a mixture that will fill and cover the scratched mark.
Here are the tools you need:
- Scratch repair polyurethane marker/pen
- Clean rags
- Mineral spirits
- A clean bowl
Here is a guide for this fix:
- Damp a rag with mineral spirits.
- Use the dampened rag to wipe the abraded spot on polyurethane.
- Place the tip of the polyurethane marker pen where the scratch spot begins.
- Press the marker pen to release the mixture.
- Move the pen along the scratch line while pressing it.
- Stop at the end of the scratch, and wipe the pen’s tip with a rag.
- Wipe the surface to remove excess filler.
- Leave the spot to dry.
- Once dry, sand the spot with very fine-grit sandpaper.
- Wipe the dust off, and the scratch should be removed.
2. Sand and Touch up The Finish
A layer scratch is when the abraded spots have penetrated the polyurethane finish but don’t affect the wood or stain. To fix this, you must sand the surface to level the area. After, you can touch up polyurethane by applying 2 coats.
Tools you need:
- Polyurethane paint
- 320-grit sandpaper
- Clean rags
- A paintbrush
Here is a guide for this method:
- Wipe and clean the affected spot.
- Sand polyurethane with fine-grit sandpaper.
- While sanding, inspect the surface often, so you don’t sand into the wood.
- When you have leveled the polyurethane with the depth of the scratch, stop sanding.
- Remove dust.
- Re-apply 1-2 coats of polyurethane.
- Leave the finish to dry.
3. Strip and Re-Seal The Wood
If the abraded or scratches spots have affected the wood, remove the polyurethane, apply wood filler, and re-seal the wood. These deep gouges on wood are often caused by dropped items or heavy furniture.
Tools you need:
- Sandpaper of different grits
- Wood filler
- Polyurethane paint
- Wood stain (optional)
Here is a guide to this method:
- Remove polyurethane by sanding or applying paint stripping compound.
- Fix scars in the wood with wood filler.
- Sand wood with fine-grit sandpaper to remove imperfections.
- Remove dust.
- Apply wood stain (optional).
- Re-apply polyurethane.
- Allow the finish to dry.
Scratches Between Polyurethane Coats
You can’t fix scratches between polyurethane without removing at least one coat. So, if you notice a scratch on the polyurethane finish, you must sand it until it’s leveled with the scratch. Afterward, you must fill or fix the spot and re-apply polyurethane.
You can’t fix the scratch by applying more polyurethane if the scratch is between coats. That’s because polyurethane is a clear coat and will show imperfections, such as abraded spots after it dries.
To hide abraded spots between coats of polyurethane, you must apply a tinted polyurethane coating. The tinted finish will hide the abraded spots, making the surface look smooth.
- For floors, place a transparent carpet over the finish to protect it from scratch marks.
- Don’t drag items across the polyurethane finish.
- Always use the right sandpaper while sanding the finish.
- Don’t use the wrong cleaning products as they can soften the finish, making it more prone to scratches.
- Don’t use abrasive pads or cleaners while cleaning the surface.
- Wipe and clean the finish regularly.
To fix light scratches, use a scratch-fix pen to touch up the areas. To fix deeper scratches, sand the polyurethane until it’s leveled with the scratch, fix the surface, and re-seal the wood. And, to fix abraded spots under the polyurethane (wood), remove the finish, apply wood filler, and then re-seal the wood.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,