Why Does My Resin Turn Yellow?

Why Does My Resin Turn Yellow?

You pour epoxy with perfect clarity, it dries beautifully, but after a few weeks, your once-clear resin may turn into yellow resin, which can be frustrating to see. Epoxy yellowing is one of the most common issues resin artists and makers face, especially in the UK, where we deal with a mix of damp weather and occasional bursts of strong sunlight.

The good news? With the right knowledge of the science and the application of the correct methods, yellowing can be eliminated or at least reduced. This manual discusses the reasons which make epoxy resin yellow and provides you with tips you can use in practise so that your resin projects retain their crystal clear appearance many years into the future.

Why Epoxy Resin Yellows

1. UV Light Exposure

The main cause of epoxy yellowing is the UV rays. Epoxy also breaks down gradually when in the sun, just like fabric and fades into a dull amber colour.

2. Heat & Oxidation

High temperatures speed up oxidation, a chemical reaction where resin molecules break down and discolour. This is common on tabletops, coasters, or countertops exposed to kettles, mugs, or sunlight through a window.

3. Low-Quality Resin

Not all resins are formulated the same. Cheaper products often lack UV stabilisers or non-yellowing additives. These may look fine at first but quickly degrade with exposure.

4. Moisture & Environment

Humidity and moisture can interact with epoxy hardeners, leading to cloudiness and early discolouration. In the UK climate, this factor is often overlooked.

How To Prevent Yellowing Of Epoxy Resin

1. Select a Resin of high quality and UV protection.

Start with the right base. One of the stabilisers added to a high UV-resistant epoxy resin reduce the process of yellowing remarkably.

• Look for terms like UV resistant, non-yellowing, or stabilised formulation.
• Products like Res-iT UV Resistant Epoxy Kits are designed for crystal-clear results and long-term clarity.

2. Apply a Protective Topcoat

An epoxy coating is not sufficient when it is under sunlight. Coating with a UV blocking topcoat, e.g. polyurethane, acrylic, or automotive clear coat is your project sunscreen.

• In case of furniture and the countertops, a polyurethane coating will be useful.
• In the case of art or decorative work, acrylic spray sealants are lightweight and good to use.

3. Keep Resin Out of Direct Sunlight

Placement matters. The so-called UV resistant resins will all turn yellow after sometime when left in direct sun.

• Store resin table, tray and coasters out of bright south facing windows.
• Do not keep resin art in the open all the time.
• In jewellery, shop items should be kept in pouches or boxes when not in use.

4. Avoid Excess Heat

High heat accelerates chemical breakdown. Common mistakes include:

• Placing hot mugs directly on resin coasters without heat-resistant backing.
• Positioning resin furniture near radiators or direct sunlight.
• Using epoxy in outdoor conditions without extra protection.

Hack: On surfaces such as countertops, one should always use heat-resistant mats or coasters to increase the lifespan of the finish.

5. Correct Mixing Ratios

Improper resin-to- hardener ratios can leave epoxy chemically unstable, which speeds up yellowing.

• Measure accurately with digital scales or measuring cups.
• Mix slowly and thoroughly to prevent streaks of unmixed resin.

6. Store Resin Correctly

Even untouched bottles of resin may turn yellow in storage in case of improper handling.

• Keep away in a cool, dark, dry location.
• Keep bottles tightly sealed.
• Do not keep close to windows or heaters.

How to Fix Yellowed Epoxy

It is too late to prevent sometimes. Even when your epoxy is already yellow, there is still a possibility of saving your project.

Sand & Recoat

• Wipe the surface using fine-grit sandpaper (320600 grit).
• Wipe off using isopropyl alcohol.
• Apply new UV-resistant epoxy and preferably a topcoat of UV.

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Use Pigments or Tints

In case the yellowing is not severe, one can add a tint or pigment to cover the discolouration. The appearance can be refreshed by using metallics, opaque colours or alcohol inks.

Practical Example: Resin River Tables in the UK

River tables are a popular UK project. Because they are large, they are often placed in well-lit living rooms. Without UV protection, that “crystal clear” river will eventually turn amber.

• Use a UV-resistant deep-pour epoxy.
• Finish with a UV-blocking topcoat.
• Keep away from direct sun exposure, use blinds or window films if necessary.

Final Checklist: Preventing Epoxy Yellowing

• Choose UV-resistant, high-quality resin.
• Apply a UV-blocking protective topcoat.
• Avoid direct sunlight and high heat.
• Mix accurately and store resin correctly.
• Recoat or repurpose yellowed projects when needed.

Conclusion

Yellowing of epoxy is very annoying, and it does not necessarily spoil your projects. By using the correct resin, protective finishes and maintenance of your resin art, furniture or jewellery, you can significantly lengthen the durability of clarity and beauty of your piece.

Buy smart, protect well, and your epoxy resin projects will stay crystal clear for years.

Explore our UV-Resistant Epoxy Resin Kits to keep your creations protected from yellowing.