Does resin get soft in the sun?

Resin is a great product to use outdoors. However, if you’re using it in a hot climate or leaving it out in the sun for long periods, you may notice that your resin gets soft and bendy.

This can be frustrating! Here’s everything you need to know about why this happens and what you can do about it:

Why does my resin get soft in the sun?

Resin is a chemical reaction, and sunlight is a catalyst for this reaction. When resin reacts with UV light from the sun, it gets soft in the sun.

The resin’s reactivity will depend on the base material you use, but generally speaking, if you’re using something that contains polyester resins (like polyester hardener), your resin can be used in the sun without breaking down too quickly.

If you’re using something like epoxy or polyurethane-based hardeners instead of polyester ones, then your product won’t be as resistant to UV radiation and will break down more quickly when exposed to direct sunlight for extended periods of time.

What happens to resin in the sun?

Resin is a thermosetting polymer. This means that resin contains cross-linking sites, which are chemical groups that react with other molecules and create bonds between them when the resin is heated or exposed to UV light.

Once you’ve exposed your resin to heat or UV light, it will not harden again—you’ve permanently changed its chemical structure!

In addition to being sensitive to heat, thermosetting polymers are also sensitive to oxygen and moisture in their environment: once you pour your casting mold material into a container of some sort (like a cup), air contact with the liquid surface will cause oxidation and degradation over time.

Why does my resin get bendy in the sun?

Have you ever noticed that your resin can get bendy in the sun or heat? That’s because when the temperature is above 32 degrees Celsius, it will start to become soft.

When it goes below 32 degrees Celsius, it will become hard again. This is because of a chemical reaction called polymerization – when two or more molecules join together to form a bigger molecule.

This process happens naturally when you mix together resin and hardener as they react with each other and form more complex molecules that make up your finished piece!

While this may sound complicated (it really isn’t), there are some tricks you can use if you want to avoid having this happen:

  • Don’t leave unfinished pieces out in direct sunlight while they’re still curing – wait until all layers have dried before moving them around
  • Place finished pieces somewhere where they won’t be affected by wind or humidity (like an enclosed cabinet)

Can you put resin in the sun?

Yes! Resin can be used outdoors and even in direct sunlight. The finished product will be extremely durable and long-lasting, so it can handle just about any type of weather.

However, as always, we recommend that you store your completed project indoors where humidity is controlled and temperature is stable.

Is resin waterproof? No, but it does have a high resistance to moisture absorption thanks to its thermoset nature.

You can use this type of polymer without worry about damaging your creation if it gets wet or is exposed to water for prolonged periods of time (again – don’t leave it out in the rain!).

Does resin soften in heat?

Resin is a thermoset, which means it’s a material that has been cured by heat. Thermosets don’t soften in heat or hot water; they’re made to be rigid and hard.

This is super important because if you’re working with resin, you do not want your project to end up as a gooey mess!

So if you live somewhere very hot like me (I’m from Texas), I recommend keeping your workspace cool so that the resin will cure properly.

Why did my resin not harden?

It’s important to remember that resin is a product and like all products, it can go wrong. To get the best results from your resin, it’s important to use the right type of resin for your project and make sure that you mix it properly.

  • Check if you have used the right kind of resin. Resins come in two main types: epoxy or polyester. They both harden when they are cured with UV light but they cure at different rates depending on their chemical composition and how long they have been mixed.
  • Make sure your mixture is not too thin or thick by using a stick to mix both parts together for several seconds until there is no more separation between them before pouring into molds or onto objects (if applicable).
  • Make sure your mixture does not contain any contamination from dust particles which could prevent proper curing when exposed to heat during curing process (typically 20 minutes under direct sunlight).

Does epoxy resin fade in sun?

Resin is a type of plastic that can be used to fill in gaps, make casts and harden into a solid form. When you purchase this resin, it comes in two parts: one part catalyst and one part hardener. You mix these together and then apply them to your project.

To do this, you may use an old paintbrush or putty knife to spread the mixture onto whatever surface you are trying to fix or repair.

When exposed to UV rays from direct sunlight, as well as other sources such as fluorescent lights, epoxy resins will harden quickly but they will also become brittle over time so they need protection when being stored outdoors or within reach of direct light sources (like window sills).

Can resin be used outdoors?

Resin is not UV resistant. Over time, the sun will cause your resin to get cloudy, soft and bendy (which is called “blooming”), sticky and brittle.

Resin can weather beautifully over time, but if it gets too hot or cold while curing it can be ruined. If you’re using your finished piece outside where there might be a lot of direct sunlight on it all day long, that could cause the resin to warp or soften.

If you want to use a piece outside like this then I recommend using acrylic paint instead of resin (but make sure they’re UV resistant!), or just covering it up with something like an umbrella so that only parts of your project are exposed at any given time!


You can use resin to make all sorts of things, but you need to know how it reacts to the sun so that you don’t get frustrated with your projects.

You can expect your resin to get bendy or soft in the sun, but if it gets too hot then it will start to break down and become unusable as a hardening agent.

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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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