Can Thinning Epoxy Affect Colour or UV Stability?

How Thinning Can Affect Clarity and Colour

Adding thinners to epoxy may seem like a convenient way to reduce viscosity, but using too much can have noticeable consequences. Excess thinner may cause your finished resin to appear cloudy rather than crystal clear, and can sometimes alter or dull the tones of added pigments. To keep clarity high, opt for resins that are already designed with low viscosity for your application—rather than adding solvents yourself.

Thinning and UV Stability

One of the main drawbacks of thinning epoxy resin is a potential reduction in UV resistance. Properly formulated UV-stable resins include additives that help guard against yellowing and fading over time. Thinning the resin can dilute these protective qualities, making your piece more prone to discolouration when exposed to sunlight or fluorescent light. For projects where UV stability is important, consider using products such as “Epoxytable 10-Ten”, which contains strong UV filters and is designed for lasting clarity.

When This Matters

• Clear finishes and art: For river tables, jewellery, and artworks where transparency is essential, avoid thinning the resin yourself and use a UV-stabilised, low viscosity epoxy instead.
• Outdoor or sunlit items: Yellowing risk increases with thinners, so always choose a resin specifically formulated to resist UV exposure for these applications.