Why does epoxy turn yellow?

You might have noticed that a piece of epoxy is yellowing and wondered why it does this. This article will explain what epoxy is, what causes yellowing, and how to prevent or reverse it.

Epoxy is a chemical compound made of 2 parts: resin and hardener. When the resin and hardener are mixed together they produce strong bonds which can be used in many applications including coatings, adhesives, flooring, encapsulation, and more.

Epoxy can be clear or pigmented with colors (tints) added to create colored epoxies. The color options are limitless; this means you can find a color to match your project perfectly!

When new or fresh, most types of epoxies appear clear or translucent with just a slight tint to them depending on whether they were originally pigmented with colors at all before being applied anywhere in particular like so say over top some concrete floor surface area for example…

Why does epoxy turn yellow?

Yellowing occurs when epoxy is exposed to UV light, heat, oxygen, and moisture. These factors are all part of the natural yellowing process that takes place as epoxy ages.

The good news is that there are ways to slow down this process in order to keep your epoxy looking clear for as long as possible!

Is epoxy still good if it turns yellow?

The short answer is: no, it is not bad. It might look bad though.

When applied to a surface and left to cure, epoxy can turn yellow over time. This discoloration is unavoidable and cannot be prevented.

Fortunately, the yellowing does not indicate that the epoxy has become unsafe or lost its ability to protect your floor as it was intended to do.

Epoxies are made up of two parts: resin and hardener (also known as the curing agents). When these two parts are mixed together, a chemical reaction begins which slowly transforms them into the final product – hardened epoxy coating.

During this process—more commonly called ‘curing’—a tiny portion of each part will react with oxygen in the air instead of mixing with the other part, resulting in polymerization; essentially causing some of the material to dry at a superficial level while deeper layers continue to cure/harden properly.

The color change observed during this first step is irreversible because it occurs on an atomic level within individual molecules of resin and hardener (see figure 3).

This phenomenon can affect all epoxies, regardless of manufacturer or type; however, certain formulas are slightly less prone than others to changing color when exposed to ultraviolet light (or sunlight). An easy way to minimize this effect is simply keeping your floor indoors so it won’t be exposed very often!

Why would epoxy turn yellow?

Yellowing, also known as “ambering,” is a natural chemical reaction. It can be the result of two things: UV exposure or oxidation.

When the resin or hardener is exposed to oxygen, it causes a yellow discoloration.

This happens when epoxy comes into contact with air even after it’s fully cured.

What epoxy does not yellow?

Here is the good news. If you have yellow epoxy it still works fine, it just isn’t as pretty anymore. Epoxy does NOT become unsafe to use with age or exposure to UV light – what happens is that it gradually takes on a yellow color, and becomes less clear.

If you want to avoid having epoxy turn yellow, there are several things to keep in mind:

  • use additives – keep in mind that not all additives will prevent the epoxy from turning yellow (see section above for details)
  • keep your epoxy away from the sun and UV rays if possible. You can do this by using UV-protected epoxy and/or covering your project with a dark cloth when not working on it. Keep in mind that some additives don’t work well with covered/dark colors and may cause bubbles (see section above for details).
  • UV protected epoxy is available but costs more than regular epoxy

In summary, if you are looking for long term stability of color, consider using UV protected epoxy or dark protective covers (although note that some additives do not work well with dark colored surfaces so be sure to test them out first).

What if my resin turns yellow?

Resin is not naturally yellow. If your epoxy has turned yellow, it means that it has been exposed to UV rays. Resin hardeners, like the ones used in epoxy resins, are photochemically reactive to ultraviolet light and will change color when exposed to an intense light source, like the sun.

To avoid this discoloration keep your workspace dark during the curing process and use a UV blocking resin or resin with high resistance to UV exposure so that you can enjoy your epoxy masterpiece for years to come.

How do you fix yellow epoxy?

If you want to keep yellow epoxy from forming in the first place, you can:

  • Use a UV protected resin. This is probably the best option if you want to avoid yellowing epoxy or at least reduce it. If it’s already yellow, you can use this for future projects to help prevent further yellowing and make it less obvious.
  • Use a resin with a warmer color, to begin with instead of clear epoxy. Epoxies that are red or brown will still turn yellow over time but not as much as clear epoxy so it won’t be as obvious when they do start to turn yellow. These will also not be translucent anymore once they turn yellow so you may have an issue with seeing through them if that’s important for your project.
  • Use a tinted epoxy instead of a clear one — the tint will disguise some of the yellowing and make it less noticeable if your piece does start turning colors over time. However, this only works with very light tints which don’t completely obscure what is underneath them (or else you wouldn’t see any color change anyway). Anything darker than that would affect how well the underlying object shows through, making this solution only useful for very specific applications where both opacity and translucency are important qualities of the final product..

How do you get the yellow out of resin?

The yellowing of epoxy resin is a chemical reaction called oxidation, which occurs when the molecules in the resin are exposed to oxygen.

Simply put, it’s a natural process that happens over time that causes the color of your resin to change. It is not due to a manufacturing defect or poor quality control.

In fact, curing can take days or even weeks. And while the time it takes for your resin to cure depends on many factors (for example, thickness and temperature), there are things you can do if you want to slow down the yellowing process.

Does Famowood epoxy yellow?

Famowood is UV resistant and will not yellow when exposed to sunlight. This makes it perfect for projects that are going to be left outdoors, such as outdoor tables or bar tops. However, if your project will just be inside, Famowood is also an excellent choice because of its smooth, high-gloss finish.

Due to its casting properties, Famowood can also create an ideal coating for 3D printed objects. With Famowood you can achieve the clear coating that 3D printed models need in order to look their best!


So there you have it. Epoxy will turn yellow over time, but it’s still safe to use and can be fixed with a bit of elbow grease.

If you’re looking for epoxy that won’t turn yellow, check out some of the modern formulas that are designed for UV resistance.

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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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