Yellowing — Causes, Prevention, and Product Choice

Craft Resin epoxy is yellowing-resistant, but no epoxy resin is completely immune to yellowing over time. Understanding what causes it helps you choose the right product and keep pieces looking clear for longer.

The two main causes

1. Light exposure over time. All epoxy resins can gradually yellow or amber with prolonged exposure to sunlight and UV light — this is a property of epoxy chemistry generally. Pieces displayed in direct sunlight for long periods will yellow faster than pieces kept out of direct sun.
2. Overheating during cure. Pouring too thick in one go, or pouring a large volume without managing the exothermic heat it generates, can cause discolouration or yellowing as part of the cure reaction itself — this is separate from light-related yellowing and happens during the pour, not months later. See our Deep Pour depth article for layering guidance that avoids this.

Product choice

Table Top and Deep Pour are formulated for higher yellowing resistance than standard coating grades (manufacturer statement, no test method given). Arts & Crafts and UV Resin are yellowing-resistant: they help resist yellowing over time, but no resin prevents it entirely.

Reducing light-related yellowing

• Keep display pieces out of direct, prolonged sunlight where practical — a spot near a window rather than in direct sun extends clarity.
• For pieces that will live somewhere sunny, consider a protective topcoat or varnish if your project allows for one.

Reducing heat-related yellowing during cure

• Follow the layer depth guidance for your batch size (see our Deep Pour article) rather than pouring the maximum thickness in one go for large projects.
• Work in a temperature-controlled room and avoid pouring in very hot conditions, which can compound the resin's own curing heat.

If a piece has already yellowed

Yellowing that has already happened in cured resin can't be reversed by cleaning or re-coating with clear resin — the discolouration is within the cured layer itself. For pieces where clarity is critical, a fresh coat is typically applied over (not instead of) the yellowed layer if the project allows for it, or the piece is remade with the light and heat precautions above in mind.

Related articles

• Deep Pour — Maximum Depth, Layering, and Cooling Time
• Heat Resistance — What Temperature Can Cured Resin Handle?
• Shelf Life and Storage — How to Check, How to Store