Spar urethane is a popular wood finishing product that is mostly used to seal outdoor furniture and woodwork due to its excellent protection over weather elements.
Have you ever thought of applying spar urethane over paint? I did. Some people questioned my decision since the wood is already coated with paint and they said there was no use for it.
But I got amazing results by applying spar urethane with the advice from experts. Spar urethane helped to protect both pain and the wood underneath. Here’s how I did it.
Let’s figure out, Can you use Spar urethane on painted wood?
Yes, you can use spar urethane on painted wood only if the paint is fully dried and cured. Spar urethane makes a protective coat that protects both paint and wood from weather elements and UV light while removing uneven and cloudy finish on the paint. Apply a thin coat of spar urethane on painted wood.
There’s a lot more you need to know about using spar urethane on painted wood.
In this article, we’ll explore whether can you use spar urethane on painted wood, how to apply spar urethane on painted wood, how long should you wait before applying spar urethane over paint, and a lot more.
Furthermore, I’ll answer some frequently asked questions as well.
Let’s jump in!
Can You Use Spar Urethane On Painted Wood?
You can use spar urethane on painted wood with no issues. Spar urethane helps to remove the unevenness and cloudiness from the painted wood and gives a glossy, fresh look to the paint.
Plus, spar urethane makes a protective coat over painted wood. This protective coat of spar urethane helps to protect painted wood from moisture, water damage, high humidity, temperature levels, extreme weather conditions, and UV light.
Spar urethane basically protects paint and wood both from weather elements. This helps to keep your painted furniture and woodwork outdoors without any issues. Spar urethane coat protects them.
Once you apply spar urethane over painted wood, the chemical ingredients inside react with the outside air upon curing and polymerize into a super hard protective layer over the surface.
This polymerized protective coat work as a barrier to moisture and other elements.
Spar urethane makes painted wood waterproof and seals it by isolating it from outdoor elements.
Overall spar urethane increases the durability of painted wood while enhancing the painted wood’s appearance.
Spar urethane stick well onto the painted wood.
Two types of spar urethane can be used over painted wood. they are,
- Oil-based spar urethane on painted wood
- Water-based spar urethane on painted wood
Let’s see how each one of them works over painted surfaces.
Oil-Based Spar Urethane On Painted Wood
You can use oil-based spar urethane on painted wood. It protects the painted wood. remove the uneven and cloudy finish from painted wood and protect the painted surface from weather elements.
Oil-based spar urethane makes a thick coat over painted wood with excellent stability. You don’t need to apply many coats of spar urethane to get your desired finish.
But on the other hand, oil-based spar urethane gives amber/ yellow tone to the painted wood. This can be a problem especially if you’re willing to apply oil-based spar urethane over white-painted wood.
Oil-based spar urethane gives amber/yellow tone while slightly darkening the painted wood.
Therefore, thick twice before using oil-based spar urethane on painted wood.
Don’t worry! Water-based spar urethane for the rescue.
Water-Based Spar Urethane On Painted Wood
Water-based spar urethane works on painted wood with no issues. It enhances the wood’s appearance by removing unevenness and cloudiness from the finish.
Water-based spar urethane protects the painted wood to tolerate extreme weather conditions like rain, snow, high-temperature levels, and UV.
Most importantly, water-based spar urethane does not give amber/yellow tone to the painted wood. It is a clear finish.
Water-based spar urethane does not change the color of painted wood. No discoloration will happen with water-based spar urethane. Therefore, water-based spar urethane is the best finish for white-painted wood.
In terms of functionality, both oil-based spar urethane and water-based spar urethane are the same.
But in terms of appearance, water-based spar urethane has an advantage over oil-based spar urethane due to its clear finish.
As a summary, here’s how water-based and oil-based spar urethane work on painted wood.
Oil-Based Spar urethane And Water-Based Spar Urethane on Painted Wood
|Oil-Based Spar Urethane||Water-based Spar Urethane|
|Give Amber/yellow tone to the wood||Clear, transparent finish|
|Darkens the wood slightly||Provide a natural clear finish|
|Makes a thick coating||Makes a thin coating|
|Susceptible to dents||Susceptible to scratches|
|Takes more time to cure||Takes less time to cure|
|Difficult to clean||Easy to clean with water|
|Need less number of coats||Needs more coats|
|Provide excellent protection over elements||Provide excellent protection over elements|
|Enhance the wood’s appearance||Enhance the wood’s appearance|
Now you know which spar urethane you should go with over-painted wood.
Both oil-based and water-based spar urethane serves best when it comes to protection. They are just slight differences due to the final appearance.
Does Spar Urethane Stick To Paint?
Spar urethane sticks to the paint so well. painted surfaces already have adhesive properties to bond with spar urethane.
But make sure to clean the painted surface well before applying spar urethane, dust, and debris since they interrupt the adhesion between the painted surface and the spar urethane layer.
Spar urethane contains UV inhibitors that block harmful UV from hitting the painted wood which protects painted wood from fading and prevents the discoloration of the paint.
Therefore, you don’t have to worry about placing painted furniture outside under direct sunlight after finishing with spar urethane. It won’t fade or discolor due to the spar urethane coat on top.
Plus, spar urethane help painted wood tolerate extreme weather conditions such as rain, snow, and high-temperature levels. This is so useful to protect exterior painted furniture and projects.
Spar urethane seals the painted wood and is waterproof. Even though paint coat already provides some sort of protection from water, spar urethane improves it.
Overall, spar urethane help painted wood to last long and strong. It makes painted wood durable with excellent resistance to dust, dirt, fungus, mud, mold, and mildew.
How Long Should Paint Dry Before Applying Spar Urethane?
Let painted wood dry and cure for 2 to 3 days before applying spar urethane.
Some paints dry faster but some take time. Apply thin paint coats to dry and cure faster and more efficiently.
After 2 to 3 days, check the dryness of the painted surface. Apply spar urethane only if the paint is super dry and cured.
Applying spar urethane on wet paint can damage both the paint coat and spar urethane coat, ruin the wood’s appearance and kill their performances.
This drying time can differ due to the environmental humidity and temperature levels. Therefore, don’t be hurry to apply spar urethane just by depending on numerical values.
Some paints take 14 days, 30 days, 60 days, or even longer to cure.
But you don’t need to wait for that long to apply spar urethane. Just check the surface after 2 days after applying paint and start applying spar urethane if it is dried completely.
Check the painted surface closely by yourself and decide to apply spar urethane when it is completely dried.
Tools And Materials To Apply Spar Urethane On Painted Wood
- Spar urethane (oil-based or water-based)
- Painted wood
- Bristle brush or sprayer or wipe on cloth
- TSP (Trisodium phosphate)
- 120 grit sandpaper
- 320-grit or 400-grit sandpaper
- Lint-free tack cloths
- Clean rags
- Latex gloves
- Face mask
How To Use Spar Urethane On Painted Wood?
Applying spar urethane over paint is easy if you followed the correct procedure. Always check the dryness of the painted surface before starting the project.
Here’re the steps you need to use spar urethane on painted wood,
- Ventilate the area
- Surface preparation and cleaning
- Sanding the painted wood
- Apply the first coat of spar urethane
- Let it dry properly
- Light sanding of the coat
- Apply more spar urethane coats
- Let the coats dry and cure
Let’s discuss, each of the above steps one by one to get a crystal clear idea about the application process of spar urethane over painted wood.
1. Ventilate The Area
First, you need to take your painted furniture or woodwork to a well-ventilated area before applying spar urethane to it since good air circulation is a must for fast and efficient drying.
Generally, spar urethane is thick and takes a lot of time to dry and cure. Having good air circulation is a plus point since that helps to avoid many issues like forming blotches, streaks, and tacky surfaces.
Plus, working in a well-ventilated area helps to remove harsh chemicals and fumes that release upon the application of spar urethane quickly from the working area.
Those harsh chemicals and fumes can cause skin and eye irritations and breathing issues. Having good air circulation helps to keep the breathing air clean and healthy.
- Generally, we thin oil-based spar urethane with mineral spirits and water-based spar urethane with denatured alcohol before applying it on wood since thinning spar urethane increases the evaporation speed of the finish and makes it dry faster and more efficiently.
- But when we’re working on painted wood, we cannot thin spar urethane since mineral spirits and denatured alcohol can dissolve paints and peel off the surface.
- Therefore, don’t thin spar urethane when before applying it to paint.
- But on the other hand, since we’re not thinning spar urethane, it will take more time to dry and can cause surface blotchiness quite easily.
- Therefore, working in a well-ventilated area with good air circulation significantly help the drying process and minimizes the troubles.
2. Surface Preparation And Cleaning
Now clean the entire painted wood surface to remove dust, dirt, debris, and grease. Dust and dirt prevent spar urethane from attaching to the painted wood surface.
Clean the entire area with clean rags to remove dust and dirt. Saturate a clean cloth with TSP (Trisodium phosphate) and wipe on the painted surface to remove stubborn dirt and grease.
Make sure to wear latex gloves when working with TSP since it is a powerful cleaning product.
Use detergent to clean new paint and TSP to clean old paint to remove all the stubborn dirt and residues.
You can also clean the surface by wiping it with a cloth after dipping a lint-free tack cloth in warm water.
Once you’re done with the cleaning, the surface needs to be super clean and nice with zero dust and residue.
3. Sanding The Painted Wood
Now you need to lightly sand the painted wood with 120 grit sandpaper. Make sure to apply little pressure on sandpaper and keep the same pressure when sanding the whole surface.
Sanding with little pressure give adhesive properties to the painted wood which helps the spar urethane coat to stick better onto the surface.
Sanding with coarse grit sandpaper or with high pressure can damage the painted wood by peeling off the paint and ruining the wood’s appearance.
Sanding helps to remove deep scratches and flatten the sheen on painted wood.
The main purpose of sanding is to smoothen the painted wood surface and to build good adhesion between spar urethane and painted wood without layer separation.
Once you’re done with sanding wipe and clean the entire painted surface to remove dust and residues.
Leaving dust on the surface after sanding prevents spar urethane from bonding with the paint.
Now your painted wood is super ready to take on spar urethane.
4. Apply The First Coat Of Spar Urethane
You can apply spar urethane on painted wood using 4 different methods. They are,
- Using sprayer
- Wiping on
Select the way that suits you the most. With a sprayer, you can easily get a thin coat of spar urethane which help to dry faster.
You can use oil-based or water-based spar urethane on painted wood. Oil-based spar urethane leaves a yellow tint on the surface and water-based spar urethane gives a clear finish.
According to my experience, water-based spar urethane is better for pale color painted wood or white-painted wood. Oil-based spar urethane is good for bright color paints.
Apply a thin coat of spar urethane along the direction of the wood grain over the painted wood to get an even and smooth finish without forming blotches and streaks.
When you’re brushing, brush with even strokes and catch runs. Make sure not to miss any spots.
Applying spar urethane along the wood grain with even pressure gives even color all over the wood with no random splotches.
Since spar urethane won’t absorb into the wood underneath due to the paint topcoat, it will start to make a protective coat over the painted wood soon after you apply the first coat.
Let spar urethane on painted wood for 30 minutes to set and settle and wipe the excess using a clean rag.
Removing excess is helpful to make a thin even looking cot over painted wood.
- Don’t shake the spar urethane container or can during the application process since bubbles can get inside the coating and cause dumps on the finished painted wood surface
- Use a quality bristle brush when finishing painted wood with spar urethane since cheap synthetic brushes contain lots of room for air which may release and trap inside the finishing coat upon using it.
5. Let It Dry Properly
After applying the first coat of spar urethane on painted wood, let it dry for 24 hours before applying the second coat.
Keep painted wood in a dust-free, ventilated environment when spar urethane coat drying. Drying time can vary on the environmental humidity and temperature changes.
During the drying time, spar urethane makes a protective coat over painted wood by evenly spreading it all over the wood.
It will remove the cloudiness on painted wood and make the finish more even. Plus, it will improve the wood sheen and give fresh, glossiness to the painted surface.
Generally, oil-based spar urethane takes more time to dry than water-based spar urethane since oil-based spar urethane leaves a thicker coat.
After 24 hours check the dryness of the surface and move into the next step only if the surface is fully dried.
6. Light Sanding The Coat
Once the first coat is fully dried, lightly sand the entire spar urethane coat with 320 grit or finer sandpaper.
Sand lightly along the direction of the wood grain to get even looking finish without leaving any sanding marks or scratches on the surface.
Sanding gives adhesive properties to the existing spar urethane coat which helps the next spar urethane coat to stick well onto the previous coat with no layer separations.
Plus, sanding smoothens out the surface and help to get a nice, even-looking thin surface by eliminating brush marks, bumps, residue, and dust nibs.
Once you’re done with light sanding, clean the entire surface with clean rags by wiping and move on to the next step with a nice and clean surface.
7. Apply More Spar Urethane Coats
Now apply the second spar urethane coat over the first one along the direction of the wood grain without missing any spots.
Apply a thin coat of spar urethane to get even looking nice finish with a good sheen.
Likewise, apply at least 3 coats of spar urethane on painted wood to get a durable, strong finish with an enhanced wood appearance.
You can apply a maximum of 5 coats of spar urethane on painted wood. but make sure to apply thin coats and let each coat dry completely before applying another to get an even finish with no blotches.
Plus, light sand between each coat with fine-grit sandpaper builds good adhesion between surfaces and improves the wood sheen.
8. Let The Coats Dry And Cure
After applying 3 to 5 coats of spar urethane on painted wood, let yeh final coat dry and cure completely before using the furniture or wood.
Let the spar urethane applied to pained wood to dry for 24 hours and cure for 2 to 3 days.
Spar urethane will settle on the pained wood upon drying and reach its final state upon curing.
When curing, spar urethane hardens to a super protective coat which works as a barrier to the outside elements like moisture and UV light.
Curing time can vary on the environmental humidity and temperature changes. Sometimes it may take more than 30 days.
Check the status of the surface after 2 to 3 days and don’t use it until the surface is fully dried. Give an extra 2 to 3 days and check again.
You don’t need to sand the topcoat of spar urethane since we won’t apply another one above it. So, no need to make it adhesive.
You’ll notice spar urethane improves the wood sheen upon curing. Oil-based spar urethane gives amber/yellow tone to the painted wood.
Water-based spar urethane gives a clear finish.
Let each spar urethane coat dry well before applying another. Applying spar urethane on a wet surface ruins the wood’s appearance and won’t give good protection to the pained wood.
Once the spar urethane hardens fully on pained wood, the pained wood will be waterproof and isolated from outdoor elements. It will be completely protected from UV, moisture damage, water damage, insect attacks, cracks, and other elements.
That’s it, folks! Now you know how to use spar urethane on pained wood without messing things up.
Follow the above procedure and get promising results.
What Are The Best Spar Urethane Products To Use Over Painted Wood?
I have worked with several spar urethane products that work well on painted wood.
I have noticed that almost any spar urethane product work well on painted or stained surface if you follow the correct procedure.
Here’re some of the best spar urethane products to use over painted wood,
- Minwax Helsman Spar Urethane
- Water Based Helsman Spar Urethane
- Spar Urethane – Olympic Stains
- Ultimate Spar Urethane
- BHR Oil-Based Spar Urethane
- Rost-Oleum Spar Urethane
Let’s answer some frequently asked questions.
When To Apply Spar Urethane On Paint?
Apply spar urethane on paint when the paint is fully dried and cured. After applying paint let it dry and cure for 2 to 3 days before applying spar urethane.
When the paint is fully dried, that’s when you should apply spar urethane to the paint.
Never apply spar urethane on a wet pained surface since that can ruin the appearance of pained wood and reduce the performance of the spar urethane coat.
Plus, applying spar urethane over paint can cause fading and discoloration of paint.
Can I Put Spar Urethane Over Acrylic Paint?
Yes, you can put spar urethane over acrylic paint since spar urethane can remove the dullness and improves the wood sheen.
Acrylic paints have dull looking dark color, but by applying spar urethane they will get sheen and darkness will be removed.
For a clear coat, apply water-based spar urethane, and to get an amber tone, use oil-based spar urethane.
Spar urethane makes a protective coat over acrylic paint that helps to protect both paint and the wood underneath from weather elements such as moisture, high humidity levels, water damage, and UV light.
Plus, spar urethane hides dents and cracks on the surface and protects acrylic paint from insect attacks.
Spar urethane makes the acrylic paint smooth and nice while restoring the color of acrylic by removing the dullness and dryness on the surface.
Make sure to apply spar urethane once the acrylic paint is fully dried and cured on the wood. applying spar urethane wet surface can ruin the wood’s appearance.
Can You Use Spar Urethane On Chalk Paint?
Yes, you can use spar urethane on chalk paint. Spar urethane increases the chalk-painted wood’s durability and enhances the wood’s appearance by improving the wood sheen.
Use water-based spar urethane on chalk paint to get the best-performing results.
Using oil-based spar urethane on chalk paint will give amber/yellow tone to the wood and the chalk paint may peel off over time.
Spar urethane protects chalk paint from environmental elements such as moisture, high humidity, and temperature changes, UV light.
After applying, let chalk paint dry and cure for a couple of days and apply spar urethane once the chalk paint coat is fully dried and cured.
Apply a thin coat of spar urethane over chalk paint to get a nice even looking finish with an attractive sheen on the wood.
Can You Use Spar Urethane On Enamel Paint?
Yes, you can use spar urethane on enamel paint. Spar urethane improves the wood sheen and makes a protective coat to protect enamel paint from moisture and UV light.
If the enamel paint is too gloss, light sand to reduce it and make the surface more adhesive. Then apply spar urethane evenly over enamel paint to get a nice-looking finish.
After applying, let the enamel paint dry and cure for a couple of days and apply spar urethane once the enamel paint coat is fully dried and cured.
Can You Use Spar Urethane Over Spray Paint?
Yes, you can use spar urethane over spray paint. Let the spray paint dry and cure and then apply a thin coat of spar urethane on it.
Spar urethane protects the spray paint from moisture and UV light. it makes the spray-painted wood waterproof and also improves the wood’s appearance.
Can You Use Spar Urethane Over Shellac?
Yes, you can use spar urethane over shellac. Apply a thin coat of spar urethane over the shellac when the shellac coat is fully dried and cured.
You can fix the white marks on the shellac surface using spar urethane. Plus, it makes a protective coat over shellac that protects shellac wood from moisture, water damage, and rotting.
Plus, it improves the wood sheen and gives glossiness to the shellacked wood.
How Many Coats Of Spray Urethane On Painted Wood?
Apply 3 to 5 coats of spar urethane on spray-painted wood. Apply thin coats and let each coat dry properly before applying another.
Apply each spar urethane coat along the wood grain to get even looking finish and light sanding helps spar urethane coats to stick well onto the previous coat with no layer separation.
Can You Use Spar Urethane Over White Paint?
Yes, you can apply water-based spar urethane over white paint since it gives a clear finish upon curing.
Never apply oil-based spar urethane over white paint because it will leave amber/yellow tone on white paint upon curing.
Can You Put Spar Urethane Over Stained Surfaces?
Yes, you can put spar urethane over stained surfaces. Spar urethane makes the stained surfaces waterproof and protects them from weather elements such as moisture and UV light.
Apply spar urethane once the stained surface is fully dried and cured. Apply a thin coat of spar urethane along the direction of the wood grain for even looking finish.
Spar urethane makes a protective, hard coat over stained wood and improves the durability of the stained surface.
Likewise, you can also use, polyurethane over painted surfaces as well.
Did I cover all you wanted to know about: Using Spar Urethane On Painted Wood
In this article, we have deeply discussed about using spar urethane over painted wood. we talked is spar urethane is good to use over painted wood and how to apply spar urethane properly over pained wood with tips and techniques.
Spar urethane works perfectly on pained wood by improving the wood sheen. It removes the cloudiness and unevenness on pained wood. spar urethane protects painted wood from moisture and UV light. it makes the painted wood waterproof. Apply thin coats of spar urethane and lightly sand between each coat for a nice, even finish.
Furthermore, I’ve answered some frequently asked questions as well.
Hope you gathered valuable information about applying spar urethane over pained wood and its benefits.
Try to apply spar urethane over your painted wood, especially before keeping them outside to withstand extreme weather conditions.