Polyurethane is a clear coat that protects surfaces from moisture, water, scratches, and other damage. So, can you apply polyurethane over gel stain?
You can apply polyurethane over gel stain. That’s because polyurethane and gel stain have similar formulas (make-up). Gel stain is also called gel polyurethane due to the high amount of urethane in it.
Oil-based polyurethane sticks better to gel stain than water-based polyurethane. That’s because the oil-based polyurethane and gel stain use the same type of solvent (water).
Gel Stain Dry Time Before Polyurethane
Gel stain must fully dry (cure) before applying polyurethane over it. It takes gel stain 72 hours to cure and 24 hours to dry. Gel stain has a slow dry time because it uses oil as its solvent and has a thick flow.
For the gel stain to dry, the solvent must evaporate. However, the evaporation process is slower since gel stain uses natural or synthetic oil as its solvent. Also, gel stain has a thick flow; this slows the evaporation process even more.
For gel stain to cure, the solvent must evaporate, and the coating must oxidize. Once the gel stain coating oxidizes, the coating becomes hard and rigid, preventing moisture from passing through. The slower the stain dries, the more time the gel stain coating has to dry, harden and become rigid. So, the slower the dry time, the stronger the finish is.
If you apply polyurethane before the gel stain is fully dry, the finish will turn tacky, and polyurethane won’t stick. That’s because the gel stain isn’t hard (rigid) enough to hold the polyurethane coating.
To speed up the drying time of gel stain, apply thinner coats or increase the evaporation rate.
Types of Polyurethane To Use Over Gel Stain
The best types of polyurethane to use over gel stain are oil-based, exterior, or spray polyurethane. That’s because these types of polyurethane have the same solvent as gel stain (oil). This makes gel stain and oil-based polyurethane compatible.
You can also use water-based polyurethane over gel stain, but the adhesion won’t be good. That’s because water-based polyurethane uses water as its solvent. And oil and water aren’t compatible. The finish might turn sticky, tacky, or peel off if you apply water-based poly over gel stain.
To seal outdoor gel stain surfaces, use exterior polyurethane. That’s because exterior polyurethane has more additives that make the sealant more durable than other types of poly.
How To Apply Polyurethane Over Gel Stain?
Applying polyurethane over gel stain is the same as applying it over paints.
Here are the tools you need:
- A paint scraper
- A paint shield
- A can of spray polyurethane
- Fine-grit sandpaper
- A bottle of white spirit
- A hairdryer (Optional)
Tip: Prep your workspace by covering walls and floors before spraying polyurethane.
1. Degrease and Clean the Gel Stain
First, degrease and clean the gel stain coating. This removes oily scum and dust from the coating, preventing good paint adhesion. The polyurethane finish won’t dry evenly if you don’t clean the gel stain.
To degrease (clean) gel stain coating:
- Apply white spirits over the gel stain.
- White spirit isn’t strong enough to remove the gel stain, so it will remove the dirt only.
- Use a soft brush to wipe off the dirt.
- Remove the residue of the white spirit with clean water.
You can use white vinegar or soapy water as an alternative to white spirits. You shouldn’t use rubbing alcohol (unless diluted) or turpentine to clean a gel stain coating, as these solvents are too strong and can remove the entire coating.
2. Sand the Surface
Once the gel staining is dust-free, sand the coating. Sanding will remove imperfections and buff the gel stain for the polyurethane sticks better.
Also, gel stain has a glossy finish that prevents polyurethane (or other paints) from sticking properly. However, sanding removes the glossy finish of gel stain and allows polyurethane to stick to a textured (scratched) finish.
To sand gel stain before polyurethane, use 320-grit sandpaper.
3. Thin the Polyurethane
Liquid (or normal) polyurethane has a thick flow. Therefore, you must thin polyurethane before applying it with a sprayer, paintbrush, or roller. That’s because getting an even and smooth finish with a thick polyurethane is harder. If you are using spray-on polyurethane, skip this step.
To thin water-based polyurethane, use water. To thin oil-based polyurethane, use mineral spirits. If you use a spray gun, thin polyurethane with a ratio of 4:1 (4 parts polyurethane, 1 part paint thinner). For a paintbrush or roller, thin polyurethane with a ratio of 3:1 (3 parts poly, 1 part paint thinner).
4. Apply Polyurethane Over Gel Stain
Once the gel stain coating is cleaned and sanded, apply the thinned polyurethane. Oil-based polyurethane sticks better to gel stain than water-based polyurethane.
To apply polyurethane over gel stain:
- Use a sprayer, roller, or paintbrush.
- Apply 3 coats of polyurethane.
- Sand between coats of polyurethane with ultra-fine sandpaper. Don’t sand the final coat.
- Remove dust.
- Wait until one coat dries before applying the next one.
- Allow the final polyurethane coating to dry fully (cure) before using it.
Gel Stain vs Gel Polyurethane
Gel stain has a high level of urethane in its formula. The high amount of urethane makes the gel stain durable and water resistant. Because of its formula (make-up), gel stain is often called gel polyurethane.
To stick gel stain and polyurethane don’t penetrate the surface. Instead, these two finishes stay on top of the layer and stick. But, gel stain and gel polyurethane are different. Gel stain offers a softer finish than polyurethane. Also, gel stain enhances the color of wood, while polyurethane is a clear coat that doesn’t have a color.
While gel stain is durable enough for indoor surfaces, you must seal gel stain for outdoor surfaces. That’s because gel stain isn’t durable enough to withstand weather elements for too long.
Related Read: Can You Apply Polyurethane Over Tacky Stain?
Applying Gel Stain Over Polyurethane
You can apply gel stain over polyurethane. This is because gel stain and polyurethane have a similar formula (make-up). Also, gel stain contains a high amount of urethane, so polyurethane and gel stain are compatible.
Gel stain doesn’t need to penetrate the surface to stick. Instead, gel stain stays at the top layer of a surface and dries (sticks) there. Gel stain is a topical stain. And, as a topical stain, gel stain doesn’t need to penetrate to stick.
You can mix polyurethane and gel stain to get a durable and colorful finish. The gel stain has paint pigments that deepen the wood color.
You can apply polyurethane over gel stain. That’s because polyurethane and gel stain have a similar formula. But, you must prep the gel stain before applying polyurethane over it.
You can also use gel stain over polyurethane. That’s because gel stain is a topical stain and doesn’t need to penetrate polyurethane to stick.