Clear resin turning yellow – reasons for yellow resin

why is my resin yellowUnfortunately, resin kits don’t always stay clear. If you are asking yourself, why is my clear resin turning yellow, here’s what is happening:

In a resin kit, the hardener is most likely to yellow first. While the resin part will eventually yellow, the hardener yellows more quickly.

Resin kit components will turn yellow for two reasons:

1. The kit is old. You should use epoxy resin kits produced within one year of manufacture. I recommend only buying enough resin that you can comfortably use within six months, knowing that you can go a little longer if necessary. Like whoever throws out unused resin?

2. The kit is oxidizing. Open bottles allow the exposure of the liquid to oxygen in the air, causing them to turn yellow. After opening a resin kit, you should use it up as quickly as possible, preferably within thirty days.

Pro tip: It has been my experience that the ‘big box’ crafting supply stores don’t always do the best job of rotating resin kit stocks. I’ve heard from several customers how their excitement in working with resin turned to disappointment when their resin kit looked something like a doctor’s office urine sample when they got it home. To say I am over the top fussy about rotating stock on the resins sold at Resin Obsession is an understatement. Know that if you buy resin from us, you can be assured of the freshest, clearest quality resin anywhere.

So what should you do with yellowing resin?

Great question! Here’s what I do with yellowing resin.

If it has been properly stored, your clear resin that is turning yellow is still likely to cure. Use it for your resin projects that you are going to color anyway.  Here are the results of using yellow resin in a casting project.

Moving forward, buy smaller resin kit sizes that you can use within 30 to 60 days of opening. For example, instead of buying a gallon kit of resin that will take you six months or more to use, buy four sixteen-ounce kits of resin. Then, use a kit completely before opening a new kit.

Have more beginner questions about resin?  Grab a copy of Resin Fundamentals.  It’s the PDF book that will take you from confused to confident with resin in an afternoon!


Unpublished Blog Posts of Resin Obsession, LLC © 2020 Resin Obsession, LLC

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24 thoughts on “Clear resin turning yellow – reasons for yellow resin

  1. I made a white cup for my husband this past summer and now it is ugly and yellowing. How can I make sure white cups don’t turn ugly yellow?

    1. Hi Sylvia, unfortunately, all resins are going to yellow over time. Resins with UV inhibitors and stabilizers help extend the time before yellowing occurs. However, things such as mixing off ratio (even though it still can cure without tackiness), putting over an improperly cured lacquer, excessive heat, and or constant exposure to sunlight can speed up the yellowing process. How long the epoxy will last in its clear state is very difficult to predict.

    1. Jan, in my opinion, it’s because it is not cured all the way. I also use UV machine and if I take piece out too soon, it will have stickiness, but after curing longer, it’s nice and hard. Hope this helps.

      1. Yes, thank you but the ones I took out already I used clear nail polish on them and it solved the stickiness problem, have you tried this?

    2. I make about 500 resin based pendants a month using non UV resin. 1. If you are placing resin over a painted surface make sure the acrylic paint used has dried-water, moisture and resin don’t get along! At 12 hours after resin coat, my items are only slightly sticky and at 24 wearable and at 48 solid 2. Measuring-I use 2 5 cc syringes which allows for accurate measurements. 3. Curing occurs in a room that is 74-78F. 4. Resin stored at the same temperature in tightly closed bottles in a dark area.

  2. Just out of curiosity, if I use a hand-pump screwed into the top of the resin and hardener jugs, does that cut down on the exposure to air (and subsequent yellowing) after opening the resin and hardener bottles the first time? It seems like it should, but maybe it doesn’t really help much?

    1. Hi Cindy, while these pumps are great for working with large bottles of resin and hardener, they don’t do anything to reduce the amount of air in the bottle.

      1. After opening, squeeze the excess air out of the bottle then screw lid on firmly preventing the air from returning. This will help.

        1. Hi Billy, I can certainly see where this would be helpful when the bottles are full or almost full. Thanks for sharing your insight!

  3. Seems like it would be more efficient and less costly if they packaged these in air tight flexible packaging that can be squeezed out and have a valve that doesn’t allow the air to flow back in. Just a thought.

    1. Hi Susan, wouldn’t that be nice? Resin packaging has to be able to safely ship via courier in addition to meeting safety regulations. Unfortunately, flexible packaging doesn’t do well in those circumstances.

  4. I use a 1:1 epoxy clear resin…I purchased some of your UV resin for a project I needed to dry quick. My question is m; acrylic paint works great as pigment for that resin can I use in your resin too? Or will it inhibit curing?

    1. Hi Dhyana, I’m not sure I understand your question. Are you asking about using acrylic paint to color UV resin? If so, I don’t have any experience in that situation.

  5. Katherine, it’s so nice that you have this Q&A and that you take the time to answer these questions. It is so helpful!

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