Yellowing — Causes, UV Protection, and Product Choice

Craft Resin is formulated with UV stabilisers for anti-yellowing protection, 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. UV exposure over time. All epoxy resins can gradually yellow or amber with prolonged exposure to UV
light — this is a property of epoxy chemistry generally, and Craft Resin's UV stabilisers are designed to
slow this process significantly compared to resin without anti-yellowing protection. Pieces displayed in
direct sunlight for extended 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 UV yellowing and happens during the pour, not months later. See our Deep Pour depth
article for layering guidance that avoids this.

Reducing UV yellowing

• Keep display pieces out of direct, prolonged sunlight where practical — a spot near a window rather than in direct sun extends clarity.
• Consider a UV-resistant topcoat or varnish for pieces that will live somewhere sunny, if your project allows for one.
• All Craft Resin formulas already include anti-yellowing UV stabilisers as standard — no extra additive is needed for normal indoor use.

Reducing heat-related yellowing during cure

• Follow the layer depth guidance for your casting 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's 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 UV/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