How to Fix Yellowed Epoxy - Don't Toss Away!

If you find that your resin (mostly part B) is yellowed, first thing you have to do is to check if your bottle turned yellow... well...just kidding. Let's get down to business now.

You may have heard the yellowed resin can no longer be used so you just toss them away. However, that's not true at all. Stop doing this! It is important enough to mention even if your epoxy is expired, it can still be used because the chemical reaction will still take place and It will indeed cure properly as expected. Also, it won't look nearly as yellow when mixed with clear epoxy.

Why My Hardener Turned Yellow

The yellowing process comes from the oxidation of the hardener, which is natural once you opened the epoxy. If the bottle has been opened, it will yellow more quickly and looks more conspicuous in bulk or large containers.

💡P.S. Every epoxy has its own shelf life and physical properties will change over time. IntoResin's shelf life is 6 months unopened and 3 months once opened. If the resin has expired, it may look more dark yellow than natural oxidation and can still be used with dark pigments.

One thing that would cause the hardener to turn yellow is UV ray. UV ray and hardener are not friends and it would accelerate the yellowing speed of the hardener bottle. So keep in mind that store your resin in a cool and dry place and keep them away from direct sunlight.

How to Fix Yellowed Resin

It's quite a relief to hear that yellowed resin in bottle can still be used. There are a few methods that can easily and effectively help you keep your resin as clear as can be.

  • Measure how much resin you need for your projects. Use IntoResin calculator to measure exactly how much resin you need for your project and get optimal resin volume to avoid long-term storage.
  • Do not open the bottle unless you're ready to use the resin. Once received the resin you bought online, do not open it first if you are not going to make your resin projects right away.
  • Cover the lid to reduce the oxygen exposure. Every time you've finished pouring, cover the lid as soon as possible to prevent the oxygen running into the hardener.
  • Try to keep your resin away from direct sunlight. Store your resin in a cool and dry place.

Hope this article can be a lifesaver on your project! Don't bother to buy a whole new bottle of hardeners! Happy crafting!


Is UV resin more yellow-resistant than epoxy?

The answer is YES. The chemicals that make up UV resin is more stable than epoxy.

Is it possible to use UV resin to coat epoxy to avoid yellow?

Yes, it is possible to protect the epoxy surface with a UV coating.

Back to blog


@Lisa The parts are generally measured by weight instead of volume during production. The hardener is generally lighter than the resin part. So you’ll probably always have extra hardener left instead of resin if you measure by volume. Do you measure your resin by weight or volume? You can also ask the epoxy brand you used if they sell extra part B. We IntoResin did sell extra part A or B, but we don’t suggest mixing different brands.

Cool…Now tell us what to do about all the leftover resin that didn’t come with enough hardener. (Yes, I mixed perfectly every time. I have been working with resin since 2014, I know what I am doing.) It’s happened with every brand I’ve bought, and it’s bad for the environment to throw it away, so I have all these bottles with an ounce or two at the bottom, taking up space, and I don’t know what to do with them.

Leave a comment

Please note, comments need to be approved before they are published.