What happens to epoxy in the sun?

You have some epoxy that you’re working on using, but you’re not sure if it will be safe to use in a situation where it could potentially be exposed to sunlight.

Maybe you’re an artist who wants to know if the work that you will create will hold up in places where people may want to display them, or perhaps you just want to know whether or not your new experiment with epoxy surfaces can stand up after being left out on the porch for a few hours.

Whatever your situation is, this article is here to address all of your concerns about how long epoxy last outside and what happens when you leave it out in the sun!

What happens to epoxy in the sun?

There is no easy answer to this question. The reason for this is that every epoxy product behaves differently when exposed to sunlight and UV radiation.

For example, one epoxy may turn yellow in the sun while another stays clear. One epoxy might become tacky while another remains hard.

It all depends on the formulation used in each individual resin product and there is no way of knowing what will happen before actually doing a test.

When formulating an epoxy system, we take several steps to ensure that it resists yellowing in order to maximize its UV resistance including using UV stabilizers as well as utilizing low viscosity and low acid number epoxies.

In addition, we use aluminum oxide pigments which are also known for their ability to resist fading and discoloration caused by UV rays.

How long does epoxy last outside?

Epoxy resin is frequently used in a wide range of applications, both indoors and outdoors. It has the ability to bond dissimilar materials together with ease, acting as a sealant or coating for anything from wood to metal, concrete, and more. The question that arises, however, is how does epoxy fare against the elements? How long does it last outside?

Epoxy can be used on almost any surface, whether indoors or outside. When it comes to being exposed to the sun however there are several things that you need to consider:

  • UV exposure and heat: How much exposure will your finished epoxy product receive when outdoors? Will it be parked under a tree or laying in direct sunlight? If you plan on using epoxy on outdoor surfaces that will see lots of UV light and heat make sure that you are using an outdoor grade epoxy. In addition, you should also try and find an epoxy system comprised of UV stable materials (UV inhibitors) if possible.
  • Coating thickness: Coating thickness is another factor that comes into play when choosing an appropriate resin for outdoor use. The thicker the coating, typically the more resistant it is against UV light because more material exists between the sunlight and substrate material itself (i.e., wood). This doesn’t mean though that thicker coatings are better suited for outdoor use as there are other factors involved such as overall quality of materials and environmental factors (temperature variations; humidity levels; etc.).
  • Resin selection: Another important consideration is what kind of resin do you want/need your finished product made out of? If you are looking for a clear finish then choosing a crystal clear resin would be ideal while using something like glow in the dark pigments might work better if visibility during nighttime hours is desired.
  • Hardener selection: Finally selecting an appropriate hardener is important when working with any type of epoxy resin but especially so when working with one that will be exposed to direct sunlight

Can sunlight damage resin?

Resin can react to UV light. If the resin is exposed to sunlight for too long, it may have a yellowing effect or cloudiness. This is why resin needs to be stored in a dark place until you are ready to use it.

This is especially important if your resin project includes layers of color that you do not want to be affected by UV rays. Use a shaded area outside if possible when creating your project and keep it indoors until it cures completely.

Any exposure will not cause damage to the piece after it has cured, but during the curing process, there can be adverse effects from being kept in direct sunlight.

Will epoxy hold up outside?

Imagine this: you’re working on a boat. The boat’s made of wood, so you apply the wood epoxy to the joints. You place it in the sun and let it set.

Two weeks later, you come back to your boat and find that all of your epoxies have turned red! You start pulling up on the boards, only to find that they’ve all separated. What happened?

It turns out, there are two main kinds of epoxy—the kind used for boats and the kind used for home improvement projects.

The first is designed to hold up in extreme weather while resisting oxidation. The second is designed to be inexpensive and easy to use which is perfect for those who don’t know much about chemistry or need something quick and cheap to use around the house. It’s also important to remember that these are two different products with different applications

Is epoxy good for outside?

Epoxy is a clear resin that has many uses, but one of its most common applications is as a protective finish for wood. However, epoxy should not be used on items that will be exposed to sunlight for several reasons: it yellows when exposed to UV light and becomes brittle over time, which can cause it to become cloudy and begin peeling.

Instead of epoxy, we recommend polyurethane for use on outdoor projects.

Polyurethane is similar in appearance to epoxy but does not yellow or become brittle in the sun. In fact, it’s designed to withstand direct sunlight so well that it can actually reflect UV rays away from the wood beneath it—an extra layer of protection against sun damage.

Long-term exposure to sunlight may still cause polyurethane to degrade eventually, but this will take much longer than with epoxy. With proper care (and possibly some regular reapplication), polyurethane should work well enough outdoors that your project will be damaged by other factors before the coating fails!

Does epoxy fade in sun?

Epoxy is a word that refers to a wide range of resins. In general, epoxy does not like sunlight. If you’re using epoxy for any kind of outdoor project, fading and discoloration may be an issue.

Fading means that the resin changes color and loses its original vibrancy. This is caused by UV rays from the sun breaking down the molecules in the resin.

The more you expose resin to the sun, the faster it will fade. Generally speaking, a clear coat of epoxy will lose its clarity faster than other types of resin (like polyester or vinyl ester).

If you’re applying a full coat of epoxy over wood as flooring or as an art canvas, this can be a problem depending on where and how it’s used.

However, if you are just coating the wood with epoxy as a sealant or varnish, fading should not be much of an issue because there is only one thin layer applied and it will not affect the appearance very much even after years in direct sunlight.

Will epoxy melt in the sun?

Epoxy resins are thermosetting polymers. These materials do not melt when exposed to elevated temperatures; they undergo chemical reactions at a very slow rate, or react quickly and cure (harden).

In either case, the material remains solid at high temperatures rather than flowing like thermoplastic polymers. Thermoplastic resins will soften and flow over time when exposed to high temperatures.

Epoxy resins that can withstand higher temperature environments are available but these products are typically modified epoxies or contain other polymer groups that allow for use in elevated temperature applications.

Does heat affect epoxy?

Epoxy is a thermosetting polymer that undergoes a curing process. When cured, epoxy becomes very hard. In some circumstances, heat can accelerate the curing process and cause the epoxy to become brittle.

The best place to store your uncured epoxy is in a cool, dark place. It’s not recommended to leave your Epoxy out in the sun or expose it to any other kind of heat source.

If you accidentally left your epoxy in the sun and are wondering if it’s still usable, check it with a stirring stick first! Put some pressure on your uncured epoxy and make sure you’re able to stir it before applying it (time is of the essence here).

If you are able to stir it without any problems, then go ahead and use the product as intended!


In conclusion, epoxy is generally a good choice for outdoor use. Epoxy will not be affected by the sun or heat. UV radiation will not cause yellowing or degradation.

The only true concern is the temperature range of application and cure. If you are using epoxy in an area that has extreme hot or cold temperatures, it is wise to choose a formula specifically designed to cure properly in those conditions.

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Martin Flood

Martin Flood has been working in the construction industry for over 20 years as a general contractor with expertise in remodeling projects that are large or small. He has furthered his career by specializing in epoxy resin flooring, providing excellent service to both commercial and residential clients. Martin’s experience enables him to offer professional advice on how to choose the right type of project based on your needs and budget.

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