Polyurethane is used as the final coat of a paint job. But, can you stain over polyurethane?
You can’t apply regular stain over polyurethane. That’s because the wood stain is a penetrating finish, and polyurethane doesn’t allow liquid to penetrate its coating. So, it won’t stick.
However, you can apply a topical stain, such as gel stain, over polyurethane. Gel stain is a topical stain that doesn’t need to penetrate the surface to stick; instead, it stays over the top layer and sticks there.
Regular stain doesn’t stick over polyurethane. Regular stain is a penetrating finish, meaning it needs to penetrate the wood pores to stick. But, since polyurethane has a coating that repels liquid, the wood stain can’t penetrate the wood and won’t stick.
If you apply it over polyurethane, the wood stain will stay over the top layer, won’t dry or stick, and will turn sticky. So, it won’t work unless you remove the polyurethane coating first.
However, you can apply gel stain after polyurethane. That’s because gel stain isn’t a penetrating finish and doesn’t need to penetrate a surface to stick. So if you apply it over polyurethane, the stain will stay over the top layer and dry there.
Polyurethane Dry Time Before Staining
Before staining, oil-based polyurethane must dry for 48 hours while water-based poly must dry for 24 hours. However, the dry time also depends on the humidity levels, room temperature, and thickness of the coat.
If you stain too soon, the finish will turn sticky and won’t dry. That’s because there will still be moisture in the coating, and the gel stain won’t stick over a wet coating. If this happens, you must remove both finishes and re-apply them.
How To Stain Over Polyurethane?
Staining over polyurethane is hard because it has a water-resistant layer that repels liquid and prevents penetration.
Note: You can only use gel stan after polyurethane, if you use other types of stain they won’t stick.
Here are the tools you need:
- Gel stain
- Foam brush or a regular paintbrush
- Fine-grit sandpaper
- Orbital or palm sander (for large surfaces)
- White vinegar or white spirits
- Painter’s tape (optional)
- A pair of gloves and breathing protection
1. Degrease The Polyurethane
First, clean the polyurethane coating to remove dust and dirt that can prevent gel stains from sticking. To clean it, use soapy water or a degreaser.
If you want to use regular wood stain, remove the polyurethane topcoat first. To do so, use mineral spirits, rubbing alcohol, or a paint-stripping compound and sand the surface.
Sanding will remove imperfections and create a textured layer for the stain to stick to.
To sand polyurethane, use 320-grit sandpaper. The fine-grit sandpaper won’t damage or dull the finish. Avoid using coarse-grit sandpaper, as it can remove or make the finish blurry. After sanding, clean the coating with a clean rat to remove the dust.
You don’t need to apply a primer or undercoat.
3. Apply The Gel Stain
To apply gel stain, use a foam brush, regular paintbrush, or rag. You need 2-3 coats of gel stain on polyurethane. If you want a dark shade for the finish, apply 5 coats.
Wait until one coat dries before applying the next coat. It takes gel stain 8-12 hours to dry enough for a re-coat.
4. Wipe The Excess
After 30 minutes of applying it, remove the excess gel stain with a rag. If you don’t, the finish will turn sticky and won’t dry because there will be too much stain for the surface to absorb.
Also, allow the finish to dry for 24 hours before using it.
Is it Necessary?
It’s not necessary to apply gel stain after polyurethane. That’s because polyurethane is a durable and strong top coat that protects the surface underneath from water, moisture, and scratches. So, it doesn’t need a protective layer over it.
However, you can apply it to increase the durability of the finish. Two coats of gel stain will add strength and durability and help the finish last longer.
You can also use it to tint the finish. Polyurethane is a clear sealant (that has no paint pigments), so its finish is transparent. However, you can apply gel stain to make its finish colorful. Oil-based gel stain comes in different colors, so you have different colors to choose from.
Note: You must tint polyurethane before applying it. But, if you forget or decide to tint later, you can apply gel stain over it.
You can’t apply regular stain to polyurethane. That’s because the regular stain is a penetrating finish, and polyurethane doesn’t allow liquid to penetrate its coating. So, they aren’t compatible.
However, you can use gel stain on polyurethane. Gel stain is a penetrating finish that doesn’t need to penetrate the surface to stick. So, it will stick over polyurethane.
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,