Can You Polyurethane Over Paint? Best Polyurethane Finishing Tips 2023

Doesn’t it always feel nice to give your living room or workspace a breath of fresh look by renovating your furniture? 

You may be looking at that old piece of painted furniture that you thought was the best color at the time of applying, but you no longer find it interesting. 

You might want a new look with different finishes like polyurethane and vanishes. But, Can you polyurethane over paint?

Yes, you can apply polyurethane over the paint; provided your paint is fully cured and clean, you can apply both oil based and water polyurethane over any wood paint. 

Even so, ensure you are cautious of discoloration, especially when using oil-based polyurethane.

First, most woodworkers love the addition of polyurethane to paint because it protects that paint and increases its durability. 

Polyurethane offers a highly resistant barrier on your painted surface, which protects it from potential damage by rain, dirt, mold, mud, or fungus. 

Also, you might be tired of repainting now and then because the paint fades away. 

Luckily, polyurethane also prevents your paint color from fading away due to exposure to the sun.

While you can apply polyurethane over your paint, ensure that you are working with the right paint to avoid undesirable finishes. 

For instance, some oil-based paints often turn to a yellowish color when coated with polyurethane. 

Yellow might not be a color preferred by everyone. To avoid this, use water-based paint when coating with other polyurethane layers. 

Let’s now get more information about polyurethane and paint.

What Is Polyurethane?

Image of polyurethane floor but Can You Put Polyurethane Over Old Polyurethane?Polyurethane is a polymer containing organic units joined by carbamate or urethane links. 

This variety of chemicals produces polyurethanes with different chemical structures used for different applications. 

Unlike other common polymers like polyethylene and polystyrene, polyurethane is a product of a wide range of starting materials.

Polyurethane, one of the most diverse forms of synthetic resin in the market, is used in unlimited household and commercial products worldwide. 

Due to its flexibility, polyurethane plastic can be tailored into several forms.

It could be as stiff as fiberglass, squishy like upholstery form, protective like varnish, bouncy like rubber, or as sticky as glue. 

All these can be tailored based on the different needs of the users. 

Therefore, it is safe to say that polyurethane’s versatility allows it to serve as paint, cotton, rubber, metal, or wood in several fields.

Scientifically, polyurethane contains two chemical components: polymers and urethane.

There are several types of polyurethane. Read on to find out!

  • Flexible Polyurethane Foam

Flexible polyurethane foam is specially designed to serve as a cushioning or protective material. 

You can find it in wood furniture, mattresses, bedding, and vehicle interiors. It is significantly used in North America as it makes up approximately 30% of polyurethane sales in the region.

From its name, flexible polyurethane foam comes in various shapes, flexibility and durability. 

Besides being lightweight and supportive, the flexible polyurethane form will give you the desired comfort.

  • Rigid Polyurethane Foam

Rigid polyurethane foam is primarily used in commercial and residential insulation. 

Most people prefer it for commercial and residential purposes because it is energy efficient and versatile. 

Rigid polyurethane foam is all-weather tolerant. It keeps buildings warm during winter and cools during summer. 

It also helps to dampen exterior noises.

  • Binders

They are polyurethane used to bind different materials. 

They make different materials, ranging from wood panels, flooring materials, and sand casting to carpet underlays. 

They are also valuable for the manufacture of several housing components.

  • Coatings, Adhesives, Sealants, and Elastomers (CASE)

CASE is a collection of polyurethanes used for covering or sealing different products. The seals are used to increase durability. 

CASE creates strong bonds between different products. They are effective for bonding products that need to be air or water-tight. 

Like other polyurethanes, CASE collections are also versatile. You can mold them into any shape. 

Also, not only are they light, but also durable, regardless of the environmental conditions.

  • Reaction Injection Molding (RIM)

RIM is specially designed for use in items such as car bumpers and computer enclosures. 

This polyurethane acts as a backup plan when injecting molding is inadequate. 

It is also used in making parts that have strength with low weight. It comes in different strengths and sizes. 

RIM parts offer dimensional stability. Its properties are equally dynamic as you can use them with sporting products, automotive manufacturers, and furniture used in day-to-day activities.

  • Thermoplastic (TPU)

This is such an elastic, flexible, and abrasive-resistant type of polyurethane. Due to its properties, it is often used in several construction and automotive applications. 

It is no wonder it can withstand different temperature ranges and their impacts. It is quite a handful! Most manufacturers prefer TPU because of its flexibility. 

You can customize TPU into the shape and color that best fits your needs. Also, one can extrude, inject, blow or compress the TPUs.

  • Waterborne Polyurethane Dispersions (PUDs)

This polyurethane is used with a water-based solvent for coating and adhesion purposes. 

They are primarily used in places of volatile organic compounds and dangerous air pollutants.

What Is Paint?

Most people think of paint as the color on their home walls, cars, bought, or caravan. However, there is more to painting than just the color. 

Paint is a material usually applied as a liquid and then dries to form a solid through various chemical processes. 

Paint combines homogenous ingredients such as binder, pigment, VOC, and additives. 

This combination forms a solid dry, adherent film following an oxidation process when applied on a surface as a thin layer. 

Depending on our unique needs, paint is mainly used for decoration, protection, identification, and sanitation. 

Paint also comes in a variety. Below are some of the types of paint you should know:

  • Oil paints. These are primarily used as a primer, undercoat, and finish coat. Oil paint has had a never-ending demand because of its durability and the glossy finish on the surfaces.

Oil paints will give you a rich finish and protect your property against water damage.

The durability ability of oil paints has made them popular for use in metals, walls, doors, windows, and stained surfaces. The paint is also highly recommended for trim work.

Expert Tip: Oil paints will work best on your wooden and metallic surfaces for home projects. This is associated with their ability to offer a strong adhesion that would last for ages.

  • Emulsion paint. Emulsion paint is a fresh touch in the market. Unlike traditional oil paints, emulsion paints are water-based with fast-drying properties.

Emulsion paint is a to-go-to choice for most paint contractors because it’s alkali resistant. It offers your surface a rich texture and a stronger color retention ability.

For this reason, emulsion paint is such a long-lasting paint choice. 

You would want to work with an emulsion paint because it is odorless and dries faster than you imagine.

Also, the acrylic emulsions will give your beautiful home undeniable resistance against cracking and a flexible finish for years.

While exposure to sunlight will leave your wall paint looking faded and undesirable, acrylic emulsions are the deal too good to refuse!

They don’t fade, even when exposed to sunlight.

  • Enamel Paint. This is an oil-based solvent with properties similar to oil-based paint. It gives you high durability, strong adhesion, beautiful and glossy finish.

It also protects your surface from stains and water damage. It is a relatively expensive choice but also worth the price.

  • Bituminous paint. It is formed using dissolved asphalt and tar, thus explaining the black, tar-like appearance it offers. Bituminous is also alkali resistant.

Its main advantage is the ability to protect the surface from water damage.

However, bituminous is not recommended for use in areas exposed to the sun as its quality diminishes with sunlight.

Let not the black or tar appearance limit you when using a bituminous paint. You can always add a pigment to achieve a color of your choice.

  • Aluminum Paint. Aluminum paint combines aluminum flakes and an oil or spirit varnish.

Ensure to read the instructions on the type of varnish to use with this paint, as they will offer you different drying periods.

We love aluminum paint for its silvery finish and durability. It is also electricity, weather, water, and corrosion resistant.

Since it is resistant to corrosion, aluminum paint is preferred for use in water tanks, hot pipes, masonry, and oil storage tank, among others.

  • Anti-corrosive paint. From its name, anti-corrosive paint prevents surface corrosion.

This type of paint is made from anti-corrosive elements like zin chrome, fine sand, and linseed oil.

They are best suited for metallic surfaces but also work well on pipes and other external structures.

It is a cost-effective paint choice that is black. It is mainly used in industrial products for protection from rust.

  • Synthetic Rubber Paint. Synthetic Rubber Pain is commonly used on concrete surfaces, walls, and floors.

It is formed by dissolving synthetic resins and the addition of suitable pigments and solvents to it.

Since you can add a pigment, you can achieve any color of your choice.

The paint has fast-drying properties and maintains consistency and uniformity on large expanses.

Other benefits of using this paint are that it is weather and chemical-resistant and also friendly to your pocket.

  • Cement/ Distemper Paint. Also known as a whitewash, cement paint is a mixture of lime, chalk, pigment, water, and glue.

It is one of the existing oldest paints in the market, which currently has been modified into paint form. Cement paint is available in powder.

It is a cost-effective medium of paint application. It does not crack on exposure to sunlight; hence you can apply it on cement and rough interiors and exteriors without primers.

  • Specialty home paints. These include antifungal, waterproofing, crack-bridging, and home paints for exterior and interior walls.

They protect your walls from climatic conditions, domestic situations, and typical wear and tear.

There are a variety of paints you can choose from, with each type serving a different purpose. Check in at your favorite local store for paint that fits your needs!

Do I Need to Sand Paint Before Polyurethane?

Sanding is crucial before applying any finish on your surface. It helps in removing dirt that would otherwise get stuck under your varnish. 

However, applying polyurethane over paint can always lightly sand your surface. 

We say “lightly” because you don’t want to remove the paint from your surface altogether, do you? 

Well, in this case, lightly scratch your work surface to create a keying surface that will enhance the adherence of polyurethane.

Use 120—a grit sanding screen. If you are working on a painted floor, scuff it with sandpaper alongside a floor buffer. 

Ensure that you have wiped off the sanding dust after you finish. Use a tack cloth or a damp rag.

How Long Should Paint Dry Before Polyurethane

It is crucial to consider the paint’s curing time before applying polyurethane. Averagely, paint often cures within 24-72 hours. 

However, the time may vary depending on factors such as climatic conditions, the number of paint coats applied and the type of paint used, among other things. 

For instance, water-based paint cures faster than oil-based paint. 

Allow your paint to completely cure before applying the polyurethane. Cleaning the paint while still wet will lead to its obliteration.

 Also, applying polyurethane to wet paint increases the risk of discoloration. The paint would also mix with the polyurethane, interfering with the intended clear coat. 

Avoid such mishaps by allowing your paint to dry within 24 hours before applying the polyurethane.

Important note: There is a significant difference between ‘drying’ and ‘curing.’ Drying describes the plasticity stage of your surface. 

Here, the surface doesn’t feel as wet as when you started applying, hence safe for handling. 

However, the product is yet to complete its full state of hardness. Test this with your fingernail. 

On the other hand, the term ‘cure’ explains the time when your paint covering has achieved the final hardness state. 

In essence, there will be no more chemical changes to the physical features of your coating.

While your paint will dry up within 24-48 hours, it will take at least 21-30 days before it cures. 

Also, note that different paint types have different curing periods. Play it safe by allowing your paint to fully cure before applying the polyurethane.

 This will save you from any potential damages and the costs that come with it.

How to Apply Polyurethane Over Paint

Since your wood is painted and ready for use, applying polyurethane over it should not take up much of your time. You will need the following tools:

  • Detergent or trisodium phosphate (TSP)
  • Water
  • A piece of tack cloth/ dump piece of cloth
  • A vacuum cleaner
  • 120-grit sandpaper for deep scratches
  • 220-grit sandpaper
  • Applicator (Paintbrush, spray, pad, or roller: whichever works best for you.)
  • Sponge
  • Protective wear, i.e., rubber gloves and goggles.

Below is a step to step guide on how to apply the polyurethane over paint.

Step 1: Surface Cleaning

Thoroughly clean your surface using a detergent or trisodium phosphate (TSP). 

TSP is commonly known as a food additive but is also an excellent cleaning agent due to its concentrated dose. 

Use the TSP if you are working with old paint and a detergent for recent paint.

Failure to properly clean your surface will prevent the polyurethane from adhering. This is because polyurethane does not work effectively on greasy surfaces.

Always wear goggles and rubber gloves when using TSP to protect yourself from harsh chemicals.

Step 2: Sanding

Sanding helps in removing any deep scratches on the wood surface. It will also help in flattening the sheen in the paint. Use 120-grit sandpaper. 

If you don’t achieve a flat smooth surface after sanding with the 120-grit, use a palm sander for better softening.

Step 3: Wood tacking

Sanding will leave some wood flakes or residue on your wood and around your working surface. 

Clean this up using a vacuum cleaner or a tack cloth.

I recommend using a damp, lint-free cloth to get rid of dust better. 

You can also dampen a lint-free cloth and use it to clean the surface. Allow your surface to dry before moving to the next step.

Step 4: Apply the First Polyurethane Coat

You can use an oil- or water-based polyurethane in this step based on the type of finish you desire.

Oil-based polyurethane work best on exterior surfaces, darker colors, and objects subjected to extreme temperatures. 

Water-based polyurethane works magic when working with interior projects, lighter-colored projects, or those that may receive knocks. 

Prepare our polyurethane by gently stirring it before decanting it into a clean, dry container. 

If oil-based polyurethane is your choice, consider thinning it with mineral spirits using a 75/25 ratio. 

Thinning allows the smooth flow of the polyurethane, thus preventing air bubbles. Water-based polyurethane does not need thinning.

Carefully apply a thin layer by dipping your brush into the polyurethane. Apply by following the grain. 

Also, use gentle strokes while aiming to get coverage. Avoid overworking the area because doing so will introduce air bubbles to your finish. 

Allow the excess poly to drip back into the tin. Avoid wiping the brush on the tin’s side because it will trap air in the bristles. 

This will get air bubbles in your finish; thus, your project won’t have the desirable perfect finish. 

You are not limited by the type of tool you can use to apply. A brush, roller, or spray would work just as fine. 

However, a synthetic brush is perfect for water-based poly, while a natural bristle works best with oil-based poly.

If you are working on a flat floor, it would be best to work with a soft nylon brush or a roller. 

Worry not if you are working on curved surfaces such as furniture! You can dip your rag into polyurethane and coat the furniture with it. 

Note: Avoid using a brush on curved surfaces, as it will create uneven and dripping surfaces.

Use the aerosol polyurethane. All you need to do is to shake it well and spray 6-12 inches away from your coating area. 

Don’t forget your safety mask and goggles when doing this! The hard-to-reach areas are also catered for.

Allow your polyurethane finish to dry before moving to the next step.

Step 5: Sand Again

You are likely to have an imperfect finish after your first coat. Don’t stress about it, as this is very normal! 

That is why you will need to sand and sand again! Once your polyurethane completely cures, use 220-grit sandpaper to smoothen the surface. 

Sanding between the coats is essential as it eliminates dust nibs, brush marks, deep scratches, and any other noticeable imperfections on your surface.

Step 6: Re-clean the Painted Surface

As discussed in step 3, sanding will leave some residue and dust on your wood surface, which may lengthen the drying period and cause an undesirable finish. 

To avoid this, clean using a vacuum cleaner or a tack cloth. Use a damp, lint-free cloth as it eliminates every fine unwanted detail on your workpiece.

Again, allow it to dry before adding the second polyurethane layer.

Step 7: Apply a Second Polyurethane Coat

We advise applying two or more coats of polyurethane, especially if you are using a water-based one. 

This will help you achieve solid protection. Use a brush or any other applicator available to apply the polyurethane. 

Remember to use gentle strokes and follow the grain.

Allow it to dry. Wait for three hours before adding another coat of water-based polyurethane. 

Wait for 8-12 hours if you are using an oil-based poly. Avoid sanding before the polyurethane dries up, as it will ruin your finish.

If you are yet to achieve your desired smoothness on this level, repeat the sanding, clean, and apply another poly layer by following steps 5,6 & 7. Do this until your surface is as smooth as you want it.

Here’s a Video On How to Apply Polyurethane Over Paint:

Why Would You Put Polyurethane Over Paint?

Polyurethane has a remarkable reputation for offering the best coating for several surfaces, including wood and concrete. 

You will achieve the following benefits if you apply polyurethane over a painted surface:

  • Durability. The material used in making polyurethane makes it highly durable. Its basic properties can be classified as a hybrid between plastic and rubber.

Unlike paint which can crack and chip, polyurethane will offer your surface solid protection against such potential damages.

The poly coating also forms a barrier that makes your paint resistant to mud, fungus, dirt, and mold, thus increasing its life span.

Also, polyurethane prevents the color of your paint from fading due to sunlight exposure. For this reason, polyurethane is ideal for a wide range of uses.

Its protective coating will last for years. You will only need minor touch-ups to maintain them in the desired shapes.

  • Chemical Sealing. Polyurethane is a to-go-to product for many property owners because it is a chemical sealant.

Its chemicals allow it to form a protective barrier that prevents your surface from moisture infiltration and its related effects.

It also protects your surface from salt corrosion and oil stains, among other factors.

Safe to say that your painted surface will not suffer damage from water, rot, and mold growth if applied with polyurethane.

The chemical sealant forms increase the durability and value of your furniture or whatever painted surface you are working on.

Besides, the polyurethane seal will enrich the color and uniformity of your painted surface.

It can effectively conceal any damage on your surface, as poly will always give you the solid color you need.

  • Protection from scratch. Unlike other standard coating and sealing materials, polyurethane offers a considerable degree of scratch resistance.

Paint alone could crack or get scratched for various reasons.

However, polyurethane can resist damage even from heavy equipment, especially those used for moving materials in industrial areas.

This explains why you commonly see polyurethane on garage floors, warehouse settings, and driveways. 

Applying polyurethane over paint saves you from the need to repaint your surface often. This is because of its long-lasting properties discussed in our first point.

It doesn’t matter how much wear and tear you subject your surface on; polyurethane would not crack nor get damaged.

Can You Put Polyurethane Over Acrylic Paint?

Yes, just like any other painted surface, you can apply both oil-based and water-based polyurethane over acrylic paint

Polyurethane will enhance your acrylic paint’s appearance and increase its durability. Just do it right, and you won’t be troubled about polyurethane damaging your paint.

You can use acrylic paint on a variety of painting surfaces.

 It is a fast-drying paint with a pigment suspended in acrylic polymer emulsion and silicon oils, plasticizers, stabilizers, or defoamers. 

Ensure you use a high-quality oil-based paint and latex primer when using acrylic paint. 

Failure to do so will translate into the paint flaking off and a terrible appearance.

Why Should You Add Polyurethane to the Acrylic Paints?

  • The polyurethane will give your acrylic paint an excellent finish. Much as poly is not completely smooth, it will provide a much smoother finish than what acrylic only would offer you.
  • Polyurethane gives life to your acrylic paint. Due to the dark, dry and dull nature of acrylic paints, you may need to add some brightness.

Besides, it will also form a protective layer that will protect the acrylic paint from dust and dirt.

  • They say that humans are visual beings. You may want your painted surfaces to look as attractive as possible.

Upon drying, your acrylic paint will look duller than they were when wet.

Restore and maintain the acrylic paint and shine with polyurethane. Your workpiece will also remain shiny for a more extended period.

Note: After applying acrylic paint on your surface, give it at least 24-72 hours before applying the polyurethane. A completely dried-up surface will give you outstanding results.

However, if your paint doesn’t dry properly, the polyurethane will interfere with the acrylic, leaving your surface rough and prone to damage.

Can You Mix Polyurethane With Paint?

As DIY workers, we always aim to achieve perfection. Now, if you want to achieve a glossy finish while protecting your surface from damage, polyurethane is our to-go-to choice. 

This may not be enough for some people as they may also want to give their surface a smooth finish and make it outstanding. 

You probably are also wondering how I apply the protective polyurethane and still achieve a smooth brush-stroke-free paint coverage onto the work.

Can we get the best of both worlds by mixing the paint and polyurethane? 

While it is possible to mix polyurethane with paint, this is usually not the best practice.

 If you don’t get this right, I hate to burst that bubble, but it would ruin your whole piece! 

Ideally, we recommend applying a paint coat first, allowing it to dry, then adding the polyurethane. 

However, if you have to do it, and are very conscious about your time, be very selective about the type of paint you mix with the polyurethane.

The general thumb is obvious! Mixing polyurethane with paint could hurt your pockets, ruining both the polyurethane and the water solution. 

This is because oil and water do not mix, resulting in clumping of the oil, which you’ll now see floating around that water. 

The same thing will happen if you mix polyurethane with paint. You are likely to end up with a clumpy and messy-looking product that will honestly be useless to you.

 If you must mix the two products, go for a water-based polyurethane, although still not recommended.

Can You Polyurethane Over Paint?

You can achieve the smooth finishing of your dreams by applying polyurethane over your painted surface. 

Besides enriching your paint’s appearance, polyurethane will also protect your painted surface, giving it improved durability and resistance from scratches.

 Remember that you need to allow your paint to cure fully before applying the polyurethane coat. 

Now, go ahead and give it a try, would you? What’s your best catch? A water-based or oil-based poly? I know mine!

Image of a woodworker wearing hearing protectors for woodworking

Tyron Otieno

Tyron is an avid woodworker and writer. He founded this website to help other woodworkers, whether hobbyists or professionals by sharing his knowledge and experiencie after a decade of woodworking.

2 thoughts on “Can You Polyurethane Over Paint? Best Polyurethane Finishing Tips 2023”

  1. My handyman has painted a courtyard fence with a stain that is brownish red but too red and too paint-like. Is there any paint, stain, polyurethane or varnish that could be applied to the fence now that could make this color more brown or towards a more natural wood look, even a bit? I’d appreciate any suggestions.

    1. Hello Liz,
      Thank for such a good question.

      There are about three methods to reduce red tone of stain on wood to brown. And considering that you have already applied red stain to your fence, the best corrective measure in your case is to apply a Green Dye.

      You could use a product like General Finishes Water Based Dye, Green. It will help turn your structure to a browner one.

      Another product you can use is Luminos LUM1106 – Kale Green – Outdoor Wood Finish Stain Protector

      Note: Check the concentration of your green dye, you can dilute it and test it on small area on your fence before applying.

      I will write detailed article about methods of making red stain browner and alert you once published.


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