Best Varnish for Epoxy Resin – What Would We Choose?

A lot of woodwork needs extra protection even after being coated with epoxy resin. They require a strong barrier against moisture and UV light that epoxy resin doesn’t provide. To help with the protection you could apply coats of varnish over the epoxy resin.

There are a few types of varnish you could apply, but what’s the best option for epoxy resin?

There are multiple types of varnish such as spirit varnish, acrylic, oil, polyurethane, and much more. The best option up to now is polyurethane varnish. Why?

Epoxy resin is a resin used mostly in wood items that are destined for outside work. That is because of its strong resistance to moisture. Epoxy cures as a hardened sealant, meaning that it can’t be penetrated easily. That’s why it’s safe to add polyurethane on top of it.

Difference between polyurethane and epoxy resin

Epoxy is a compound containing elements that give it the ability for strong adherence. It has great resistance to heat, water, and chemicals. It’s very durable and can withstand heavy weights. Polyurethane has urethane which enriches the substance’s ability for adherence more than other types of substances.

The differences between the two can be found in some aspects. Their costs differ as poly is a lot more expensive than epoxy but it ensures longevity and no need for multiple appliances over the years.

The after effect of the substances also differs. The epoxy resin becomes quite chalky when aged whilst polyurethane remains smooth. That’s why it’s a good idea to use poly as a finishing coat even after epoxy resin.

Steps to follow when applying polyurethane over epoxy resin

Before starting, you should make sure that the area you’re working on is safe. Ensure it’s well-ventilated so you don’t inhale any fumes from the polyurethane. Use a mask or a respirator, gloves, and sleeves for maximum safety.

Prepare the area

First, clean the workshop you’re working in of any dust and debris. You can use a vacuum cleaner to get the dust off and then wipe off any spots with a wet pad or a mop. Make sure you do this a couple of hours before you start work.

Prepare the wood

To make sure nothing gets stuck underneath the polyurethane, clean the epoxy resin layer. For this, use a wet cloth dampened in water. After cleaning the surface, use fine-grit sandpaper, with high grit to smoothen out any bumps in the epoxy layer. Use a vacuum cleaner to get any of the residues off so the polyurethane won’t stick to it.

Wear a mask or a respirator for the next steps.

First coat of polyurethane

To apply polyurethane there are several methods that we will go through. Depending on what type of effect you’re looking for make sure to choose the method in accordance. For example, if the area you’re working on is flat, it’s best to brush the polyurethane on. This will ensure that the coat is even and no significant bumps are left on the surface.

If the surface is contoured or uneven, it’s best to wipe the poly on so you’ll have more control over how much material you’re applying so as to not waste anything on areas that don’t need extra poly.

Lastly, if you’re working around hard-to-reach spaces in the item and you need great detailing, you should spray the varnish with a sprayer. This will apply the coat evenly around every notch of the surface and won’t leave any bubbles that will cause trouble later.

  • Brushing method

This method requires fewer coats of poly because of the brush’s thick application. It’ll be easier to cover large areas with good coat thickness.

Firstly, dip your brush in the polyurethane substance and let it soak for about one inch of the brush. Then make sure to brush it on following the grain of the wood so you don’t cause unnecessary stripes on the surface. It’s better to apply using long strokes to avoid bumps.

After applying the first stroke go back and forth in the same area to remove any drips that could have fallen whilst stroking. After you’ve coated the entire surface by brushing, ensure you leave the area to dry for about 24 hours for maximum effect.

  • Wipe-on method

If the area that needs coating is contoured, meaning it has various rises and divots, it is better to use the wipe-on method. This is because you have more control over where the poly resides in this way. It offers thinner coats that are easier to fix than those of a brush. However, you’ll obviously need to apply more coats to assure the needed thickness of poly.

To do this method, you’ll need a clean cloth or pad. Anything with soft material will do. Dip a small area of the cloth in polyurethane and begin wiping the surface of the wood. Try to use even dips for each wipe.

In the method as well, you should follow the direction of the grain so as to not cause any weird look. Make sure there aren’t any drips of poly on the area and then leave it to dry for 24 hours.

  • Spray-on method

For this method, you’ll need to provide polyurethane aerosol spray. It’s best when the item you’re coating has small detail that you wouldn’t be able to evenly coat with the other methods. It’s quite easy to apply as long as you use short bursts of spray. If you spray in long strokes, you risk dripping from the can’s tip on the surface.

Make sure you’re using the poly spray in an area that is forgiving to the spray. That means that no unwanted items are around as the spray gets everywhere. Try to spray from beginning to end to avoid making marks in the middle of the item. After each coat, leave the surface to dry before applying a second coat.

Wet sand the first layer of polyurethane

To do this, you’ll need fine-grit sandpaper. Sand the area after the polyurethane layer has fully dried. Wet the sandpaper and sand it until the surface is smooth to the touch. After sanding, wipe down the area with a wet cloth to remove the particles that have come off. Then make sure to dry the surface before adding the other layer of polyurethane as water will ruin the adhesion of poly to epoxy.

Thin the polyurethane varnish

For the second and third coats of polyurethane, it’s a good idea to water down the substance. The first coat shouldn’t be thinned down because it has to adhere well to the epoxy.

Apply the other coats

Use the same steps as for the first coat for the other coats you’ll have to add to the surface. After each coat, make sure that it’s fully dry before applying anything else. Drying time is crucial if you don’t want to make any unwanted errors while applying coats. Allow at least 24 hours of drying time for each appliance.


After you’ve decided that enough layers of polyurethane have been added to the wood, finish the project by polishing the entire area. You should use a high-quality polishing paste for the best effect on removing scratches. Do this after at least 48 hours of drying time of the last coat of polyurethane.

Are there other options for the top of epoxy resin besides varnish?

Yes, there is a bundle of other options you can choose from besides varnish.

  • Lacquer

The same as varnish, lacquer gives a glossy finish but with less longevity. It is quite thin but it shines beautifully. It’s less toxic than normal varnish so you don’t have to take a lot of precautions before applying it.

  • Shellac

This is a neutral finish composed of safe, non-toxic components. It is way safer than polyurethane and it gives a good finish look.

A problem with shellac is that it’s not very heat resistant so it can’t be used on wood that has exposure to heat. If it does then it’ll create white rings that are not pleasurable to the eye.

Final thoughts

The best type of varnish to apply over epoxy resin is polyurethane. It ensures a great finishing look, and strong resistance against UV light, heat, and moisture. It’s easy to apply and you’ll be pleased with the glossy afterlook.

If the varnish is not the way you’re looking to finish the project, then there are other alternatives for you, such as lacquer or shellac.