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Does Casting Craft Polyester Resin Yellow Over Time?

Does Casting Craft Polyester Resin Yellow Over Time?


Polyester resin is one of the most versatile materials, so it’s not surprising it’s very popular in the world of crafts. However, one of people's most common doubts about resin is whether it yellows over time. Today, we will answer that question! We will also provide a few tips to help you care for the pieces you make or get from your favorite resin craft manufacturer.

What Is Polyester Resin?

Polyester resin is a thermosetting polymer that cures into a hard, durable finish. This type of resin is particularly popular for casting, molding, and laminating because it’s very resistant. It’s also very versatile because it’s easy to work with to create many different pieces.

Does Polyester Resin Yellow Over Time?

Yes, it does. Polyester resin becomes yellow over time and this can happen due to several factors. Let’s explore each of them individually:

 1. Exposure to UV Light

When resin is exposed to UV light, its molecular bonds start to break down, leading to the yellow coloring. This process is called photodegradation. So, the more exposed your resin figures are to UV light, the faster the yellowing process will be. Additionally, the effect will be more intense if the resin itself doesn’t have UV stabilizers.

 2. Quality of Ingredients

As is the case with any other product, the quality of the materials makes a difference. When it comes to resin, you need to make sure it’s high-quality. If it’s not, it will be a lot more prone to discoloration. This is because the resin either lacks UV stabilizers or contains impurities. So, always invest a little more in your resin or make sure your resin craft manufacturer uses the best materials.

 3. Environmental Factors

Another reason why polyester resin becomes yellow over time is environmental factors, such as high humidity, temperature changes, and air pollutants. These things contribute because they can accelerate chemical reactions within the resin. This is particularly true when the material is exposed to high temperatures.

 4. Mistakes During the Curing Process

Lastly, if mistakes are made during the curing process, they will also contribute to discoloration. For example, not letting the pieces cure effectively or inaccurate mixing ratios will make the resin pieces more susceptible to yellowing. This is why it’s important to follow the instructions of the resin and invest in well-made resin pieces.

How to Prevent Polyester Resin Pieces from Yellowing Over Time

Now, the yellowing of polyester resin pieces can be prevented by doing the following:

 1. Invest in High-Quality Resin or Resin Pieces

One way to avoid this issue is to invest in polyester resin formulas that contain UV stabilizers. These additives will provide a protective barrier against UV rays, slowing down the resin's degradation process and minimizing yellowing.

We recommend choosing polyester resin from suppliers with a solid reputation and reading the product description to confirm the quality level. If you often purchase resin pieces, make sure to check that they use high-quality materials as well.

 2. Follow Instructions

When you work with resin, following the manufacturer's instructions regarding mixing ratios, curing times, and environmental conditions is essential. This will guarantee the best results and prevent yellowing. So, please read the instructions carefully and follow them closely to make sure the pieces have a long life span.

 3. Store Your Resin Pieces Properly

How you store resin pieces matters a lot! That’s something you can control to make sure your polyester resin doesn’t yellow quickly. The most important thing to do is to store the pieces in a cool place.

You should also keep your polyester resin art away from direct sunlight and UV lights. So, avoid placing your cabinets or shelves facing windows. It’s equally important to make sure that the resin you use for your crafts is stored properly. Keep it in a dark, cool, dry place. Airtight containers work very well for this.

 4. Protect the Surface of the Resin Pieces

When you’re done creating your polyester pieces, go the extra mile and apply a clear topcoat. You can also use a UV-resistant varnish for the top layer. This will give the piece some additional protection and help maintain the appearance of the piece over time. Just make sure that the topcoat you use is also high-quality.


What Can I Do If My Polyester Resin Pieces Are Already Yellow?

Unfortunately, once the resin has turned yellow, there’s no way to reverse the effect. However, you can update the piece by adding a new layer of resin. If the pieces are small and the yellowing process is only just beginning, you can try sanding off the yellow color.

The most important thing is to be proactive and take measures to prevent yellowing. Also, invest in good quality materials and choose your resin craft manufacturer carefully. For example, Ennas Gift is a great option! Browse their products here.

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