You may have seen your painted furniture peeling off, getting dirty, or fading. What’s a possible solution to prevent further damage to your surfaces? Can you put polyurethane over paint to protect it? Here are the key points you need to know based on my experience.
What is Polyurethane?
Polyurethane is a plastic substance or polymer used to make several objects differently. It can be used in foam sponges, skateboard wheels, hoses, gaskets, and spandex. You can use a polyurethane finish on a table top as it is a clear sealer on an any object’s surface.
The clear coat of polyurethane gives protection against the weather, corrosion, and other elements that can easily harm an object. A polyurethane coat that is sanded in between can also make the objects and surfaces water-resistant and scratch-resistant.
Can You Apply Polyurethane Over Paint?
Yes, you can apply both water-based and oil-based polyurethane over a painted surface. For a better and seamless finish, I highly recommend adding two or three drops of the same paint color to the polyurethane.
It not only elevates the look but also combats the risk of a cloudy or inconsistent finish on your projects.
Additionally, cleaning your polyurethane brush and clearing the painted surface is important to ensure proper adhesion of the polyurethane coat. Always ensure you clear away any dust or debris from your painted surface.
And a heads-up: if you’re applying it to light-colored paints, oil-based polyurethane can give off a yellow or amber tint. Meanwhile, water-based poly tends to stay transparent.
What Does Polyurethane Over Paint Do?
Applying polyurethane over paint enhances its longevity and resilience. I use polyurethane for a robust finish, and using it for painted surface protects it from elements like mud, rain, and dirt, and even keeping away fungus and mold.
It can also prevent color fading from being exposed to sunlight. Also, polyurethane protects your painted wood from deep scratches.
Although polyurethane is usually applied on stained wood, some DIY fans now use polyurethane over paint. However, if you do not want a yellowish finish or a color change, you should use a water-based polyurethane product.
How Long Should Paint Dry Before Applying Polyurethane?
Most paints should be allowed to cure for more than 4 hours before applying a coat of polyurethane with a sprayer. It takes a shorter time because you don’t have to touch the surface directly. It means that the paint will not be a mess.
If you are using a foam brush or cloth to put polyurethane over paint, allow it to dry at least overnight or longer if necessary, similar to painting over wood sealer. It will prevent brush marks and uneven brush strokes. It will also avoid damage when you put polyurethane over paint.
Also, remember that temperature and humidity play a big role in the drying process of wet paint. Therefore, there is no exact time as to when you can add polyurethane. Examine the painted surface carefully and check for wet areas.
Paint can be deceptively slow to cure. Don’t hold off on applying polyurethane waiting for paint to cure fully. Just ensure you’re applying it the right way. Keep in mind, poly can take its sweet time too, often needing up to a month to truly harden and cure.
When to Apply Polyurethane Over Paint?
To prevent any damage to the painted surface, I typically wait a few hours before applying the polyurethane. However, based on the specific type of poly you’re using and your method of application, you might need to adjust the waiting time, either longer or shorter.
The safest time for the paint to dry is 24 hours. But if you sprayed polyurethane over paint, you may wait shorter than that. Remember to ensure the surface is clean and free from sanding dust and other dirt. A clean surface will help the polyurethane to hold properly.
Can I Put Polyurethane Over High Gloss Paint?
You may apply polyurethane over high gloss paints. However, you must remember that polyurethane will not stick much to shiny surfaces compared to matte, satin, and flat finishes.
Glossy and semi-gloss finishes are more durable than chalky, satin, flat, and matte finishes, so choose a semi-gloss poly finish over satin poly finish for high gloss paints.
You can also add this polyurethane type to chalk paint, acrylic paint, and water- and oil-based finishes. It will leave the surface dry, smooth, and glossy.
See Also: Can You Polyurethane Over Tacky Stain?
What Type of Polyurethane Can I Apply Over Paint and How Long Does it Take to Dry?
Painted surfaces can vary in drying times. When I work with either oil-type or water-based polyurethane on a painted surface, each takes its own time to dry thoroughly.
Oil-based poly gives an amber tint to a painted floor or painted furniture. It is perfect on stained wood.
Oil-based poly can preserve the color of the wood and protect it from deep scratches and other elements. But remember that oil-based paint does not always require oil-based polymer . (How about putting oil-based poly over water-based stains? Is it okay? Read next!)
Oil-based polyurethane dries for about six to twenty-four hours, depending on the brand. There are now fast-drying poly and oil-based paints on the market. It can take up to six hours to dry, four times faster than the regular oil-based counterpart.
The wood can be fully cured after a week or even three weeks. So, if you plan to use a brush or clean cloth to apply the polyurethane, you have to wait until the surface dries off completely, or you will ruin the whole project.
In my line of work, I often recommend water-based polyurethane for painted wooden surfaces. It dries clear and tends to dry faster. With some brands I’ve used, it can be ready in just two hours. Once it’s dry, the surface is set for a second coat.
You can already use the surface after 2 to 3 days, depending on the number of coats you applied and the traffic on the surface. Twenty-one days is what you need for water-based poly-treated painted objects.
How to Apply Polyurethane on Top of Paint: 7 Steps
Now that you have decided which type of polyurethane to apply, here are the tools and steps you need to follow in polyurethane application.
Tools and Materials You’ll Need
Step #1: Clean the Surface
A properly prepared surface is a must. Remove the dust and other debris to make sure that you will get a smoother finish. To ensure the surface is clean, use trisodium phosphate or detergent to clean.
A concentrated dose of trisodium phosphate (TSP) is a great cleaning tool for any painted surfaces. You can use detergent for fresh paint and TSP for old paint. Wear rubber gloves and goggles for protection.
Step #2: Sand
Light sanding is necessary to remove any deep scratches on the wooden surface. Utilize the 120-grit sandpaper for deep scratches to even out the paint beneath.
You might use a palm sander and lightly sand the surface if 120-grit sandpaper does not work. Too much pressure and force can cause the paint to peel off.
Interesting Read: Sanding Sealer vs Polyurethane
Step #3: Clean the Residue
Using a tack cloth or a vacuum cleaner, remove the sanding dust. Make sure to remove small dust particles as they can ruin the coat of polyurethane. You can also use a lint-free cloth dipped in warm water to wipe and clean the surface.
You can be sure that no dust particle will escape. Allow the surface to dry.
Step #4: Apply the Polyurethane
Apply the first coat of your desired polyurethane. A clear coat or an amber tint depends on the type of poly you choose. Follow the wood grain to prevent marks and uneven coats.
Applying the first coat, you can use a spray, brush, pad, or roller. Once you have covered everything, allow the first coat of polyurethane finish to settle and dry.
Step #5: Sand the Surface Once it’s Fully Dried
Once the first coat is fully cured, sand the surface using 220-grit sandpaper. It will give you a smoother texture. It will remove any brush marks, dust nibs, and other things that can make the surface look unclean.
Step #6: Clean the Surface
As you may have noticed, the surface can undergo multiple cleaning procedures. It is one of the most important things to ensure that polyurethane can adhere to the surface. You can sand the surface again or repeat step 3.
Step #7: Apply Another Coat of Polyurethane
Whether it’s paint or polyurethane, one coat is not always enough. The first coat may look good, but apply more than one or two coats for added durability and protection. A few coats can make the most difference when it comes to polyurethane.
Once you’ve laid down the second coat of polyurethane, repeat steps 5 through 7 until you achieve the desired result. If you’re working with water-based poly, I’d recommend applying at least two coats. And a little pro-tip for that final coat: make absolutely sure the surface is spotless and dry.
Why Should Polyurethane Be Applied on Acrylic Painted Surfaces?
Applying coats of polyurethane over acrylic paint can take the surface to the next level. Here are why you should consider using coats of polyurethane on acrylic painted surfaces.
What is Acrylic Paint?
Acrylic paint is made from suspended pigments in silicon oils, acrylic polymer emulsion, stabilizers, metal soaps, defoamers, and plasticizers.
In addition to being a quick-drying paint, the visual and physical properties of acrylic paint make it suitable for a variety of purposes.
When I work with acrylic paint, I always lean towards high-quality latex primer, latex paint, or even oil-based paint. Doing so has consistently helped me prevent the surface from flaking once the paint job is complete.
When dry, acrylic paints also render a softer exterior. Therefore, it easily attracts dirt and dust. That is why polyurethane can be useful for added protection.
When Can You Put Polyurethane over Acrylic Painted Surfaces?
Acrylic paints can dry within 24 to 72 hours. After the drying process, you can proceed with the application of polyurethane. The longer the waiting time, the better, especially if you are not using spray paint.
If the surface is not fully dried, acrylic paints with polyurethane will result in an even and rugged finish. It will make it vulnerable to more damage.
How to Apply Polyurethane Over Acrylic Paint
Here are the steps on how to apply poly over acrylic paint.
Step #1: Wash the Surface With Warm Water
First thing first, cleaning is the most important step in the process. Overall, it will ensure that the polyurethane will adhere to the surface and the paint will not be damaged. To clean the surface, you may use warm water. Avoid using just soap to clean the surface.
Latex remover can also affect the color of the surface or even damage it. You can get rid of paint drips using a paint stripper or sandpaper. Use mineral spirits to remove wax.
Step #2: Sand the Surface
After cleaning the surface, use 120-grit sandpaper to smoothen the texture without producing deep scratches. Use a palm sander if manual sandpaper is not enough.
Floor buffer and 120-grit sanding screen can remove uneven paints. Remove the small dust particles using a damp rag.
Step #3: Pick an Applicator
You can use a spray gun or brush to apply water-based polyurethane or oil-based polyurethane on a surface. A roller is not advisable since it can leave bubbles that can harden the shell.
Polyurethane is already thin, so there is no need for a paint thinner. Adding a thinner may cause it to be watery and run. To test, you can pour a small amount onto a surface to see if it’s thick and sufficient.
Step #4: Apply a Coat of Polyurethane, Then Scuff
Apply the first coat of polyurethane and let it dry. The drying process varies on the type of poly. Water-based poly usually dries up faster.
Once dried, scuff the surface lightly using 120-grit sandpaper to remove the uneven texture. Remove the dust using a damp cloth.
Step #5: Apply the Second Coat
Apply the second coat of polyurethane to create a more durable finish. This is enough to get the glossy and smooth finish that you like.
How to Seal Acrylic Paint with the Minwax Polycrylic Finish
To seal acrylic paint on top of the Minwax polyclyric coat, do the steps below:
Drying and Curing: What You Need to Know
How Can You Know If the Paint Is Dry or Cured?
To easily know if the paint is already dry, I firmly touch a small area. If it doesn’t feel tacky or sticky, then it’s dry.
To know if it’s cured, prod the surface using your fingernail. The paint is not yet cured when there’s an indentation left. But if the paint has been cured, you will see no marks or indentations on the surface.
Will Polyurethane Finish Stick to All Surfaces?
Yes, polyurethane will stick to almost all surfaces. But, before application, the surface must be free from any debris, grease, or wax. It should be dry as well.
Factors That Affect the Paint Drying and Curing Time
Here are some things that can affect the drying and curing period:
Different types of paints have different drying and curing time. The paint color can affect the process. Lighters shades dry more quickly than darker colors. Chalk paint, for example, takes 30 minutes to dry and 30 days to fully cure. Water-based paint takes 4 hours to dry and only 21 days to cure.
From my hands-on experience, the type of wood plays a role in how well polyurethane or paint adheres to the surface. Woods with high chemical concentrations can pose issues down the road. For instance, I’ve noticed this with Rosewood, especially those that contain aromatic cedarwood.
Temperature can help the paint to dry slowly or quickly. The proper temperature is between 70 to 77 degrees Fahrenheit. If it falls below 50 degrees Fahrenheit, the paint will have a hard time drying.
The absence of ventilation will slow the drying process. If you are in a closed space, you may use a fan to help dry the paint and get rid of the smell.
Too much moisture can highly affect the surface. Bubbles will be formed on the surface of the wood. Humidity also slows down the drying and curing processes.
The ideal humidity percentage should be between 50 to 70%. Use a humidifier if the moisture is not enough and a dehumidifier if the moisture is too much.
How to Clean Once You’re Done With Coating Polyurethane
You may use water and soap to clean up any messes if you are using water-based polyurethane. You can also use water to clean up the brushes. If you are using oil-based paints or oil-based poly, you should use mineral spirits or paint thinner to clean the brush.
Which is the Best Polyurethane Coat to Apply Over Paint?
The best polyurethane that you can apply over a surface depends on many factors. Each poly has its own best characteristics and formulation.
You must know the type of wood, paint, and finish that you want to achieve. All of these will help you find the best polyurethane over paint.
Can you apply polyurethane over latex paint?
Yes, you can add polyurethane over latex paint. Wait for the paint to dry before applying two to three coats of polyurethane.
Can you put polyurethane over stained surfaces?
Yes, you can apply polyurethane over stained surfaces. However, you need to rough up the surface by sanding to make sure that polyurethane can stick to it. You also need to take into consideration the right type of polyurethane to use.
Can you put polyurethane over painted stairs?
You can put polyurethane over painted stairs. If it is a high-traffic area, you need to apply at least 3 coats of polyurethane to make sure it is protected. Allow proper drying period between each coat.
How many coats of polyurethane can be painted on the wood and floor?
For a desirable end result, apply at least two coats of polyurethane to the wood and floor. If the surface is going to be used often, three coats is better. Water-based poly can also be applied four to five times on sheds and floors.
Can polyurethane be applied over white paint?
If you want to prevent white paint from yellowing, only apply water-based polyurethane. It will keep the surface protected and shiny without adding an amber tint.
Can polyurethane be applied over spray paint?
You can apply polyurethane over spray paint provided that you allow the surface to dry and cure. Generally, spray paints dry for about 24 hours.
Can polyurethane be applied over shellac?
Shellac can be applied over polyurethane and vice versa. However, shellac is not flexible and polyurethane is flexible. If the polyurethane moves and the shellac don’t, there will be a crack eventually.
Can polyurethane be applied over chalk paint?
Yes, polyurethane can be applied over chalk paint. It will provide a smoother and more durable polyurethane finish.
Can paint acrylic enamel be applied over urethane primer?
It is crucial to use a sealing primer to make sure that the paint and polyurethane will stick together. Since lacquer-based primer or paint and enamel or urethane paints are incompatible, using a sealer can solve the problem.
Should an acrylic painting be sealed?
Sealing an acrylic painting is essential. It will protect the painting from UV rays, dust, and even yellowing.
Does Mod Podge seal acrylic paint?
Mod Podge can seal acrylic paint. It adds gloss and protection to your projects. It will help the surface to last long.
Drawing from the insights in this guide, I’d definitely recommend applying polyurethane over paint. Once your paint is dry, cured, and free of any debris, you’re good to go with a layer or multiple layers of polyurethane. However, always ensure good ventilation as it helps the surface dry quicker.
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