Epoxy resin is a product used by many crafters across different crafting types. Whether you enjoy woodworking, acrylic painting, or creating home décor, epoxy resin can help keep your projects sealed and protected.
As with any craft product, there are pros and cons to using it. One drawback to using epoxy resin is that it will yellow over time.
So, how to fix yellowed epoxy? To fix yellowed epoxy still in the bottle, it’s best to just replace the bottle all together. To fix yellowed epoxy that has cured, you can try sanding down the top layer and pouring a new layer. The best way is to keep your finished epoxy projects away from UV light and high heat.
Yellowing in epoxy is an unfortunate but somewhat unavoidable process. There are ways you can slow it down or prevent it from being too dark, but discoloration is natural for epoxy. Let’s explore some ways you can prevent and fix yellowed epoxy.
Why Did My Epoxy Turn Yellow?
There are a few different reasons why epoxy turns yellow. For cured epoxy, the most common causes are UV exposure and high heat. For epoxy still in the bottle, the most common cause is exposure to oxygen.
The main cause of yellowing in epoxy is UV exposure. This doesn’t just refer to a little bit of sunlight, but rather prolonged and direct sunlight.
Most finishes, whether it’s epoxy or another type of sealant, are susceptible to yellowing in the sun. Discoloration is a natural process that happens to most objects exposed to prolonged sunlight.
UV exposure primarily affects cured epoxy, but may still cause slight discoloration in epoxy that’s still in the bottle.
Common places where epoxy experiences quicker and deeper yellowing are in the direct sunlight from a sunny window or outdoors.
Another common cause of yellowing in epoxy is high heat. This one isn’t as common, because not everyone has areas of high heat in their homes or natural environments.
However, if you leave a project that has been coated and cured with epoxy next to a heat vent, the repeated exposure to high temperatures will cause the epoxy to yellow over time.
Other areas of yellowing risk by high heat are in a sunny window, storing the epoxy in an attic or garage (or other area of the home that isn’t climate-controlled), or leaving it outside in areas with high temperatures like southern states.
Yellowing can also happen during the curing process if you’re using a torch. Remember that when using a torch to pop air bubbles or speed the curing process, keep the torch several inches away from the epoxy.
Before you get a chance to use your full epoxy bottle, you may notice that the hardener has started to yellow.
This happens when you’ve opened a bottle of epoxy hardener and haven’t used the entire bottle. The exposure to air can cause the hardener to begin the yellow discoloration process.
Epoxy is best used within 6 months after opening, or within 1 year unopened. You may notice yellow discoloration just before or after these time frames.
How Long Before Resin Turns Yellow?
The time before resin turns yellow will depend on whether it’s already been used and cured, or whether it’s still unused in the bottle.
As noted above, epoxy resin that has been opened in the bottle but has not been fully used will last up to 6 months. An unopened bottle will last up to 1 year.
For cured epoxy projects, the time before yellowing sets in will truly depend on the amount of UV and high heat exposure.
With prolonged UV and high heat exposure, you may notice the yellowing within just a few months. If your epoxy is stored away from direct sunlight and heat, you may not notice yellowing for a year or two.
How To Fix Yellowed Epoxy
If your epoxy has already yellowed, you may be wondering if there’s a way to fix it and preserve your project. After all your hard work, it would be a shame to simply get rid of a project just because it started yellowing.
Let’s explore your options for unused and cured epoxy that has started yellowing.
Unfortunately, if your unused epoxy has turned yellow, there’s no way to reverse that process. Once it has begun yellowing, you can’t make it clear again.
Unused epoxy that has already yellowed can be used for certain projects, but you wouldn’t want to use it on a surface that you want to remain clear.
The video below from ArtResin gives some great examples of ways you can use yellowed epoxy, such as to cover bright, colorful projects or to create alcohol ink coasters.
If you have yellowed epoxy that you can’t use for your desired projects due to the discoloration, it may be best to dispose of the unused epoxy properly and purchase new epoxy.
In the future, it may be a good idea to purchase smaller bottles of epoxy at a time. This will help you use all of your epoxy within that 6-month shelf life before it starts to discolor.
Large bottles of epoxy may save you money per ounce, but you might end up spending more money in the long run if you have to keep buying new bottles because you aren’t using it before it yellows.
There are a couple methods to fix cured yellowing epoxy, but none of these methods are guaranteed. Once epoxy has started to yellow, it will continue yellowing, so it’s best to prevent it before it starts.
If it’s too late for prevention and you want to try and preserve a project that has yellowed epoxy, the first method you should try is sanding.
This will involve sanding down the top layer of epoxy that has been most exposed to UV light and/or heat. Once you get down to the original color, you can pour a new layer of epoxy finish over the project and allow it to cure.
When your newly poured layer has cured, remember to prevent the same yellowing from happening again. Try moving your project to another location that receives less sunlight or heat exposure.
If you’d rather do a quicker method that doesn’t involve sanding and starting over, you can try using bleach or peroxide to clean the epoxy surface.
Mix equal parts bleach to water, or use peroxide, and wipe down the epoxy surface. This has been known to help some yellowed epoxy reduce its discoloration, but it isn’t guaranteed.
The best thing you can do for your cured epoxy that’s turned yellow is to move it out of direct sunlight or heat.
Although yellowing will still occur with time, this will give your project a longer amount of time before the yellowing starts settling in and becoming noticeable.
How To Prevent Epoxy From Yellowing
The best way to prevent epoxy from yellowing is to buy UV-resistant epoxy resin.
This won’t guarantee that your epoxy will never yellow; that’s impossible to accomplish. Anything exposed to UV over time will eventually discolor.
However, UV-resistant epoxy will yellow more slowly, giving you more time to enjoy your project in its beautifully finished state before it begins to discolor.
Another great way to prevent epoxy from yellowing is to keep it away from sunny windows or outdoor direct sunlight.
This isn’t always possible for home projects such as a patio table for outside or even a console table for use inside. Sometimes, the location of a project naturally will expose it to a lot of sunlight or heat.
However, if you can, try to use epoxy for items that can be stored away from direct sunlight or high heat, such as on a painting or decorative tray.
Is There Epoxy That Doesn’t Yellow?
After all this talk of yellowed epoxy, you may be hoping to purchase an epoxy that’s guaranteed not to yellow. Unfortunately, they don’t exist! Epoxy resins, no matter how UV-resistant they are, will yellow over time. It’s a natural reaction.
Your best bet is still to get a UV-resistant epoxy resin, as long as you have the understanding that this will only help slow down the yellowing process and can’t prevent it completely.
Can I Still Use My Epoxy If It Turned Yellow?
Absolutely! Although you may not get the perfect crystal-clear finish you were looking for, you can certainly still use epoxy if the hardener has turned yellow.
There are tons of projects that would be great to use with yellowed epoxy, such as any project that involves bright colors.The slight yellowing of the hardener will be almost impossible to see once it’s cured on top of a colorful project.
If your epoxy hardener has turned yellow, the main thing you should stay away from is using it on white paint. The yellowing may be camouflaged by bright colors, but it will be more obvious to see on a white project.