Can You Put Polyurethane Over Paint?

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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’s what our woodworkers have to say.

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. A polyurethane finish is a clear sealer on an 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 water-based polyurethane and oil-based polyurethane over a painted surface. To make it look better, add two or three drops of the same paint color to the polyurethane. It also prevents surfaces from having a cloudy and uneven finish. 

applying polyurethane on a cabinet

The cleaning process of the polyurethane brush and the painted surface is important to make sure proper polyurethane adhesion. Remove small dust particles and other debris on the painted surface. When applied to light-colored painted areas, oil polyurethane tends to have a yellow or amber hue, while water-based poly remains clear. 

What Does Polyurethane Over Paint Do?

Polyurethane over paint makes it last long and strong. Applying polyurethane provides a durable finish and a barrier that makes the painted surface resistant to mud, rain, fungus, dirt, and even 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. 

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.

spray painting polyurethane

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. 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 takes a long time to cure, so do not wait for it to cure before applying polyurethane. Just make sure that you are doing it correctly. Poly can also take a month to harden and cure fully.

When to Apply Polyurethane Over Paint?

To avoid damage to the painted surface, apply the polyurethane after a few hours. Depending on the type of poly you will use and your application method, the waiting hours may take longer or shorter.

spraying polyurethane to cabinet doors

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 add 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 semi-gloss polyurethane finish over satin polyurethane 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.

What Type of Polyurethane Can I Apply Over Paint and How Long Does it Take to Dry?

As mentioned above, it takes different times for painted surfaces to dry. You can apply oil-type polyurethane or water-based polyurethane to a painted surface and take other times to dry completely.

Oil-Based Polyurethane

Oil-based poly gives an amber tint to a painted floor or painted furniture. It is perfect on stained wood. 

Oil Based Polyurethane on a wooden board

Oil-based poly can preserve the color of the wood and protect it from deep scratches and other elements. Remember that oil-based paint does not always require oil-based polymer [1].

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. 

Water-Based Polyurethane

Water-based polyurethane is a good type to apply on painted wooden surfaces. It will remain clear and will also dry up quicker. Depending on the brand, water-based polyurethane can dry in just two hours. After the drying process, the surface is good for a second coat.  

MINWAX Water-Based Oil-Modified Polyurethane

You can already use the surface after 24 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.

cleaning surfaces with cloth

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. 

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 polyurethane over painted cabinet

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.

applying polyurethane with a paint roller

Apply the second coat of polyurethane, and do steps 5 to 7 again until you reach your goal. If you are using water-based poly, it is recommended that you apply two or more coats. For the final coat, ensure the surface is completely clean 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. 

painting a bedside table with acrylic paint

In addition to being a quick-drying paint, the visual and physical properties of acrylic paint make it suitable for a variety of purposes.

If you use acrylic paint, you should use high-quality latex primer, latex paint, or oil-based paint. It will prevent the flaking off the surface once the color is done. 

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.

spraying polyurethane over painted cabinet

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. 

sanding the top of a dresser

Floor buffer and 120-grit sanding screen can remove uneven paints on hardwood floors. 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. 

table with polyurethane varnish top coat

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

The drying and the curing process are very important steps before applying the polyurethane coat. Here are the things you need to know about these processes. 

newly varnished table

How Can You Know If the Paint Is Dry or Cured?

To easily know if the paint is already dry, touch one area firmly. If the paint did not feel tacky or sticky, then it is dry already. 

To know if it’s cured, prod the surface using your fingernail. The paint is not cured when there’s an indentation left. The paint has been cured if no mark is seen.

Will Polyurethane Finish Stick to All Surfaces?

Yes, polyurethane will stick to almost all surfaces. But, before the 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:

Paint Type

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. 

white drawers

Wood Type

The wood type can affect the sticking of the polyurethane or paint on the surface. If the wood has high concentrations of chemicals, then there will be problems in the long run. Rosewood is an example as some contain aromatic cedarwood.

Temperature

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. 

Ventilation

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.

Humidity

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. 

bubbles on polyurethane coat

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. 

FAQ

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. Using the right type of polyurethane is also needed.

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 the 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.

Conclusion

As discussed in this guide, it’s possible and recommended you put polyurethane over paint. You can apply a layer or layers of polyurethane over paint once dry, cured, and clean. Proper ventilation is also necessary to allow the surface to dry faster.  

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson

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