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Can You Polyurethane over Paint? – The Proper Way to Apply It

By Author Mike Bailey

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Polyurethane is a very useful product with multiple uses. For those individuals who don’t know specifically what polyurethane is, it’s a synthetic product that works in the same way as paint, rubber, metal, wood, and other materials do. It’s durable, flexible, and resilient.

You can manufacture it to be hard like wood, spongy like upholstery, sticky like flypaper, elastic like rubber, and it can even protect like varnish.

In addition to this, polyurethane will not rust, it’s not affected by mold and mildew, it can withstand extremely hot and cold temperatures, and when it comes to wet surfaces, it’s is one of the best choices to use. The best part? Polyurethane has a longer life-span than rubber, paint, foam, or other applications.

As a result, you won’t have to replace it as often. This will save you both time and money. Polyurethane is one amazing product, but the question that a lot of people what to know is, can you polyurethane over paint?

Can you put polyurethane over paint?

Why do people use polyurethane over paint? Well first, polyurethane protects your paint and makes it last a whole lot longer. It does this by serving as a highly resistant barrier which protects your paint from rain, dirt, mud, fungus, and mold. Polyurethane can even help prevent the color of the paint from fading as a result of being exposed to the sun.

Although polyurethane is mainly used on stained wood due to the durable finish it provides, some homeowners use it over paint. However, there are some oil-based paints when coated with polyurethane have been known to turn a yellowish color overtime. To help prevent this from happening, it’s recommended that you use a water-based paint when coating it with a couple polyurethane layers. So, how do you polyurethane over paint?

The proper way to polyurethane over paint

Before you add a few polyurethane layers over dried paint, you’ll need make a few preparations before you can get started. It’s important to note that your paint should be fully cured before you apply a layer of polyurethane.

Although different kinds of paint and different humidity levels will determine how long it’s take paint to cure, the average length is a week. So, to properly apply polyurethane over paint:

Step 1: Wash the surface

Grease stains, dirt, dried mud, and any sort of other filth needs to be washed off before you can apply the first coat of polyurethane. Use a soft sponge or rag and a powerful detergent to clean up the painted surface. You can take a ½ cup of trisodium phosphate and mix it with warm water. This is a really effective cleaning solution. This process helps increase the polyurethane adhesion by deglossing the finish while also cleaning it too.

Step 2: Scuff away

Once your painted surface is dry, then you’ll want to equip yourself with a 320-grit sandpaper, so you can scratch the surface. Why? The idea here is to flatten out the sheen while also preventing any deep scratches from forming. Large and/or deep scratches can be visible under the polyurethane.

When etching the surface, you can do this by hand, or you can also use a palm sander. It really depends on your preference, but if you’re wanting to apply polyurethane to a floor, it’s advised that you use a floor buffer with a 320-grit sanding screen. After you are done sanding, wipe the dust away with a damp cloth.

Step 3: Decide on an application

Choose between oil-based and water-based polyurethane. The real difference between these two polyurethanes is that oil-based polyurethane has an amber tint to it whereas water-based polyurethane is clear. In addition to this, oil-based polyurethane has a stronger scent to it and tends to dry slower than water-based polyurethane.

When applying your polyurethane, make sure you don’t use a roller. Rollers tend to leave bubbles. It’s recommended that you use either a brush or spray it on. If you do decide to spray on your polyurethane, you don’t have to thin it out. Thinning your polyurethane out can cause it to run excessively.

Step 4: Apply your first coat and then etch the surface again

Apply your first coat and then let the polyurethane dry for the time listed on the container. After your polyurethane has fully dried, you’ll want to scuff scratch up the surface again with a piece of 120-grit sandpaper. By doing this, you’ll remove small dust particles in addition to squishing and flatting any bubbles that have became hard in the finish.

Step 5: Apply your second coat

Apply your second coat. Typically, you’ll never need more than two coats. Very rarely will you ever need a 3rd. Make sure you let whatever it is you coated 24 hours to fully dry. After that, you should be good.

Mike Bailey
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