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You spent hours on a resin piece — mixed carefully, poured beautifully, waited the full cure time — and then a few weeks later it starts turning yellow or orange. It is one of the most frustrating experiences in resin art, and it is extremely common among artists in Nigeria.
The good news is that resin yellowing is almost always preventable once you understand what causes it. This guide explains every cause of yellowing resin and exactly what to do about each one.
Why Does Resin Turn Yellow?
Resin yellowing is caused by a chemical process called photo-oxidation — the breakdown of the resin polymer when it is exposed to UV light and oxygen over time. Some resins are more resistant to this process than others, and certain conditions accelerate it significantly.
There are six main causes of yellowing resin. Understanding which one applies to your situation will tell you exactly how to fix it.
Cause 1: You Are Using Industrial-Grade Resin
This is the most common cause of yellowing for Nigerian resin artists, and it is entirely preventable.
Most epoxy resin sold in Nigerian hardware stores, building material markets, and general chemical suppliers is industrial-grade — designed for flooring, construction adhesives, and coatings. This resin is not formulated for optical clarity or UV resistance. It yellows quickly, often within weeks or even days of curing, especially in Nigeria’s strong sunlight.
Industrial resins are also typically not designed for the long cure times required in art casting, and they often produce more heat during curing which further accelerates yellowing.
The fix: Switch to art-grade, UV-resistant epoxy resin specifically formulated for resin art and jewellery. At Lammiluxe Art & Craft, we stock only art-grade resin that is tested for clarity and UV resistance. Once you make this switch, yellowing caused by poor resin quality will stop.
Cause 2: Direct Sunlight Exposure
Even the best art-grade resin will yellow over time with prolonged direct sunlight exposure. UV radiation is the primary driver of photo-oxidation in all epoxy resins. In Nigeria’s climate, with intense year-round sun, this effect is more pronounced than in cooler or cloudier countries.
The fix:
- Display and store your resin pieces away from windows or in areas that do not receive direct sunlight
- If you are making pieces for customers, advise them to keep pieces out of direct sunlight
- For pieces that will be used outdoors or near windows (such as window hangings or outdoor decor), use a UV-protective topcoat spray on the finished, cured piece — this creates an additional barrier against UV degradation
Cause 3: Incorrect Mixing Ratio or Incomplete Mixing
When resin and hardener are not combined in the correct ratio, or when they are not mixed thoroughly, the chemical cross-linking reaction is incomplete. The unreacted excess — whether resin or hardener — remains chemically active in the cured piece and begins to oxidise, causing yellowing and tackiness.
This type of yellowing often happens in the first few days to weeks after curing.
The fix:
- Always follow the manufacturer’s mixing ratio exactly. Do not estimate — use a digital scale or graduated measuring cups
- Mix slowly and thoroughly for the full recommended time (usually 3–5 minutes), scraping the sides and bottom of the mixing cup
- If a finished piece is yellowing AND feels slightly tacky on the surface, incorrect mixing is very likely the cause
Cause 4: Heat
High temperatures accelerate the chemical aging of epoxy resin. In Nigeria’s climate, storing resin pieces in hot environments — a car interior, a room that gets very hot during the day, near cooking areas — will cause yellowing to occur faster than it would in cooler conditions.
Excess heat during the curing process is also a problem. This can happen when you use coating resin in a deep mold (it generates too much exothermic heat), or when you try to speed up curing by placing a freshly poured piece in direct sunlight or near a heat source.
The fix:
- Store finished resin pieces in cool, shaded areas
- Never try to speed up curing with heat — let resin cure at room temperature in a covered, dust-free area
- Never pour coating resin more than 6mm deep in a single layer — deep pours trap exothermic heat and yellow from the inside
Cause 5: Certain Pigments and Inclusions
Some colourants, dyes, and inclusions can cause or accelerate yellowing. This is less common with quality pigments but worth knowing.
Organic dyes (such as food colouring or fabric dye) are not designed for use in resin and can react with the resin chemistry, causing colour shifts and accelerated yellowing. Certain natural inclusions — fresh flowers, leaves, and organic materials — can also release moisture and chemicals that affect the resin as it cures.
The fix:
- Use only pigments specifically formulated for resin: resin pigment paste, mica powder, alcohol ink, or resin-grade glitter
- Dry all natural inclusions thoroughly before embedding in resin. Fresh flowers must be pressed and dried completely — any moisture will cause clouding, bubbling, or yellowing around the inclusion
Cause 6: Age
All epoxy resin yellows slightly over a very long period of time — this is simply the nature of polymer chemistry. However, with high-quality art-grade, UV-resistant resin and proper storage, this process takes years rather than weeks or months.
If your pieces are yellowing within days, weeks, or a few months of making them, age is not the cause — one of the other causes listed above is responsible.
How to Tell Which Cause Is Affecting Your Resin
| Symptom | Most Likely Cause |
|---|---|
| Yellowed within days of curing | Industrial-grade resin or incorrect mixing |
| Yellowed within weeks, also slightly tacky | Incorrect mixing ratio |
| Yellowed only on the surface facing the window | UV/sunlight exposure |
| Yellowing starting from the inside of a thick piece | Too much heat during curing (deep pour of coating resin) |
| Yellow spots around inclusions | Wet or fresh inclusions, or incompatible colourants |
| Gradual yellowing over many months | UV exposure over time — expected, but can be slowed |
Can You Fix Resin That Has Already Yellowed?
Unfortunately, once resin has yellowed it cannot be reversed — the chemical change is permanent. However, you have two options:
For mold-cast pieces (coasters, jewellery, etc.) — the yellowed piece generally cannot be rescued. Prevention is the only real answer.
For flat surface pieces (trays, boards, tabletops) — you can sand the surface back with fine-grit sandpaper and apply a fresh layer of high-quality coating resin as a topcoat. This does not fix the yellowing underneath, but it restores the clarity of the visible surface.
Preventing Yellowing: Quick Summary
Use art-grade, UV-resistant resin — not industrial or flooring epoxy. Measure and mix your resin accurately and thoroughly every single time. Keep finished pieces out of direct sunlight. Store resin pieces in cool environments. Use only resin-specific pigments and fully dried inclusions.
Following these five rules will prevent the vast majority of yellowing problems Nigerian resin artists face.
Supplies That Help Prevent Yellowing
Lammiluxe Art & Craft stocks art-grade epoxy resin with UV stabilisers specifically chosen because of Nigerian climate conditions — strong sunlight, high temperatures, and humidity. All resin we sell is art-grade, not industrial.
Shop now: lammiluxecraft.shop | Nationwide delivery across Nigeria | WhatsApp us for product recommendations.
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