Polyurethane Over Paint: How Long for Paint to Dry Before Polyurethane

Polyurethane over paint image

Let me get this straight – you want to apply a finish on another finish? I’m just messing with you!

Every now and then, you find that after you have painted a wooden surface, you’re not pleased with the result. It looks great, but it just feels like something is missing.

If your solution is to apply polyurethane over paint, then I salute your ingenuity.

Poly can create a unique look on any type of paint. The only thing that can go wrong is not knowing how long for paint to dry before polyurethane.

Can You Put Polyurethane Over Paint?

Yes, you can put polyurethane over paint. As long as the paint has fully cured and it’s clean, you can apply both water-based and oil-based polyurethane over any type of paint. However, you need to be cautious of discoloration, especially from oil-based polyurethane.

Now that you know it’s possible to apply poly over painted surfaces, let’s find out how long you should wait for the paint to dry before applying polyurethane finish.

How Long for Paint to Dry Before Polyurethane?

Allow the paint at least 24 to 72 hours to dry, depending on the type of paint you are using, before polyurethane. If you are not sure if the paint has fully cured, wait an extra day or two to be safe. 

When Can I Apply Polyurethane Over Paint?

As soon as the paint has cured, you can apply polyurethane finish over the paint. This is the only factor you need to consider before you apply polyurethane over paint.

On average, it takes paint 24 hours to cure, but different weather conditions and other factors can slow down this process.

It is crucial that you wait until the paint is fully cured because of the steps you need to take before applying the polyurethane finish.

You need to clean and abrade the painted surface to remove impurities before applying the polyurethane. If you don’t, the poly won’t adhere properly.

If the painted surface is still wet, the cleaning process will obliterate it and get into the wood, which can spoil it. It is important to give the wood enough time to cure – ideally 72 hours – because the surface dries quicker.

Image courtesy of thespruce

If the painted surface is dry, but the lower layers aren’t, the sanding process will reveal the wet paint underneath, and we’ll have the same problem as before.

You would then need to repaint the wood and wait for another few days before applying the polyurethane finish.

There is also the risk of discoloring when you apply polyurethane to paint. This is less likely to happen if the paint has fully cured. Otherwise, you risk discoloration, and the polyurethane could mix with the paint, and it will no longer be a clear coat.

Can You Put Polyurethane Over High Gloss Paint?

Yes, you can put polyurethane over high gloss paint once the surface is dry and fully cured. As earlier mentioned, you can polyurethane over any paints including semi gloss paints, high gloss, chalk paint, latex paint, water and oil-based paint, or even acrylic paint to attain a durable finish. Ensure you prepare the painted surface and apply the polyurethane finish correctly.

What Type of Polyurethane Can you Apply Over Paint and Their Drying Time?

You can apply any type of polyurethane over paint. Polyurethane is a clear coat finish, so it will still show the beauty of the paint beneath the scratch-resistant and waterproof covering.

Oil or Water Based: Types of Polyurethane & Drying Times

Both oil-based and water-based polyurethane do the same thing. The only difference is how they look and how long the polyurethane will take to dry.

As mentioned previously, oil-based polyurethane has an amber tint, making it perfect for applying on raw or stained wood. It gives it a distinct, darker look that will preserve the original color of the wood.

Oil-based polyurethane dries to the touch in 6 to 24 hours, depending on the type of product you use. Fast-drying polyurethane takes 6 hours, while regular poly takes at least 12 hours.

After one week of application, your woodwork is ready for light use. It then takes another three weeks before the wood fully cures.

Water-based polyurethane over paint

Water-based polyurethane is best for applying over wood because it remains clear and it dries quicker. In just two hours, the average fast-drying water-based finish is ready for a second coat.

In 24 hours, it is ready for light use and can cure in as little as 3 days. However, just like with paint, many factors can slow down the drying time. It is therefore recommended that you wait at least 21 days for the water-based polyurethane to cure fully.

How to Apply Polyurethane Over Paint

Given you have already done the hard work of making the wood usable, you won’t need to spend as much time applying polyurethane finish.

Tools You’ll Need

  • Detergent or trisodium phosphate (TSP)
  • Water
  • Water-based or oil-based polyurethane
  • Tack cloth
  • Vacuum cleaner
  • Lint-free cloth
  • 120-grit sandpaper for deep scratches
  • 220-grit sandpaper
  • Applicator – paint brush, spray, pad, or roller
  • Sponge
  • Rubber gloves
  • Goggles 

Steps to Applying Polyurethane Over Paint

Step 1: Clean the Surface

Polyurethane does not adhere properly to greasy surfaces, so you must clean the painted surface thoroughly with detergent or trisodium phosphate (TSP). While TSP is better known as a food additive, the concentrated dose is a powerful cleaning product.

Use TSP for old paint and detergent for a recent application. Be sure to wear goggles and rubber gloves when using TSP to protect yourself.

Step 2: Sand the Surface

Use 120-grit sandpaper to get rid of any deep scratches on the surface of the wood. Sand to flatten the sheen in the paint.

If you can’t get a flat smooth surface manually with 120-grit sandpaper, use a palm sander.

Step 3: Tack the Wood

Clean the sanding residue using a vacuum cleaner or a tack cloth. Make sure there is no trace of dust left, or it will ruin your polyurethane application.

You can dip a lint-free cloth in water and use it to clean the surface as well. This method gets rid of dust better, but you would need to let it dry afterward before the next step.

Step 4: Apply the First Coat of Polyurethane

Apply a thin coat of any polyurethane you want, whether oil-based or water-based, making sure to follow the grain. You can use any tool to apply the first coat – a brush, roller, pad, or spray.

Once you are done, leave the polyurethane finish to dry.

Step 5: Sand After Drying

Once the polyurethane varnish is dry, use 220 grit sandpaper to smoothen the surface. Make sure you eliminate any dust nibs, brush marks, or other imperfections such as deep scratches.

Interesting read: What happened if you don’t sand between coats of polyurethane

Step 6: Clean the Painted Surface Again

Follow the same routine as in step 3 to eradicate the sanding residue and small dust particles.

Step 7: Apply a Second Coat of Polyurethane

Generally, the first coat isn’t always enough. Apply another thin coat of polyurethane, using the same process as before. Wait for it to dry, then repeat steps 5 to 7 until you achieve the desired level of smoothness. It’s advisable to apply two coats or more, especially for water-based poly.

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

To determine if the paint is dry, firmly touch the paint’s surface in a discrete area. If the paint is not sticky or tacky, then it is dry.

To determine if the paint is cured, poke the paint with your fingernail. If your nail leaves an indentation, then the paint is not cured. However, if there is no mark, then the paint has fully cured.

It is vital that you don’t apply a coat of polyurethane varnish until the paint has fully cured. Otherwise, the cleaning and sanding process will ruin the paint and could also damage the wood.

Will polyurethane Finish stick to all surfaces?

Yes, polyurethane will stick to most surfaces. But you must prepare the surface by cleaning to remove small dust particles, wax, or grease and let the surface dry before applying polyurethane.

Factors Affecting the Paint Drying and Curing Time

1. Temperature

The first thing that will determine how quickly paint dries is heat. Just as liquids evaporate quicker when it is hot, so do wood finishes. The optimal temperature for drying is between 70 to 77 degrees Fahrenheit.

When the temperature drops below 50°F, the structure of the paint may begin to fail. Use a heat fan or HVAC to boost the ambient temperature where you are. If you have a thermostat, set the temperature at 70°F and leave the room while the paint dries.

2. Ventilation

Just as heat helps liquids dry faster, so does air. Proper ventilation will boost the drying time, just as a lack of ventilation will slow it down.

If you don’t have enough of a cross-breeze or you’re painting in a confined space, use a fan to speed up the drying process and get rid of the fumes.

3. Humidity

High humidity is a problem before you paint and after. The excess moisture can be absorbed into the wood, which will then release bubbles when you paint over it.

You would find that even after a few coats, the paint will still be bubbling and will eventually peel off. Humidity also slows down the drying process because it essentially adds more water to the liquid that’s trying to evaporate.

Use a hygrometer to measure the level of humidity. A good range is between 50% – 70%. To control excess humidity, use a dehumidifier. If the problem is too little moisture, use a humidifier.

4. Type of Paint

Some paints dry quicker than others, depending on the type, shade, and brand. In general, darker colors dry slower than lighter shades.

Different types of paint and vanish dry and cure at different rates:

  • Chalk paint – dries in as little as 30 minutes, but you should wait at least a day before applying a second coat. It takes 30 days to cure.
  • Milk paint – it also dries in 30 minutes and needs 30 days to cure.
  • Latex/water-based paint – this dries in just 4 hours and can be fully cured in 21 days.
  • Oil-based paint – this takes between 6 to 8 hours to dry and at least 30 days to cure
  • Velvet finishes – this furniture-friendly product dries in about 8 hours.

5. Type of Wood

Some woods have high concentrations of chemicals that prevent the paint from sticking properly and evaporating. Rosewood, in particular, can be troublesome, as can some aromatic cedarwood. If possible, avoid painting over this type of wood.

How to Clean up After You are Done Applying Polyurethane

You can wipe any messes on the floor with just soap and water if you are using water-based polyurethane.

Brushes can also be cleaned with soap and warm water if you are using water-based poly. However, if you’re using oil-based soak the brush in mineral spirit to clean it and keep it for use next time.

FAQs

How Many Coats of Polyurethane on Painted Wood and Floor?

You should use at least 3 coats of polyurethane over the painted surface. When using oil-based polyurethane, you might be able to get away with just two coats.

However, you might need 4 or 5 coats before you get a smooth finish when using water-based polyurethane.

Follow the manufacturer’s suggestions as some may require more or less, or read our in-depth guide on applying the right number of polyurethane coats for various situations, i.e., stairs and hardwood floor.

Can You Put Polyurethane Over White paint?

Yes, you can put polyurethane over white paint, but there is a high likelihood that it will yellow.

This is the one scenario in which even most water-based polyurethanes will yellow. In fact, many manufacturers tell you not to put it on white paint for fear you won’t like the outcome.

Learn how to spray polyurethane finish today.

Can You Put Water-based Polyurethane Over Latex Paint?

Yes, you can use polyurethane over latex and oil-based paints. You can use either oil-based or water-based polyurethane over latex paint to protect the wood. Wait for the paint to fully cure before applying poly.

However, as discoloration may occur with either type of polyurethane, test it out on an inconspicuous area first.

Can You Put Polyurethane Over Acrylic Paint?

Yes, you can apply both oil-based and water-based polyurethane over the paint. The polyurethane will protect the surface of the paint while also making it look more appealing and durable.

As long as you have properly prepared the surface of the acrylic paint, the polyurethane won’t ruin it.

Can You Polyurethane Over Spray Paint?

Yes, you can apply polyurethane over spray paint as long as you have given it time to cure. Spray paint needs at least 24 hours to dry, but wait for 72 hours. You should never rush the application of polyurethane on other finishes.

Cured Paint is Poly-Friendly Paint

As you have seen in this article, you can apply polyurethane over paint as long as it has cured. We have also made the important distinction between drying and curing, so you don’t end up ruining your painting job.

If the paint is taking too long to dry, you now also know what to do to speed up the process.

With all of this knowledge at your fingertips, it is time to put it to the test. But first, you need to decide – will you be using water-based polyurethane or oil-based polyurethane? I know what I’d choose…

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