My clear resin came out yellow / cloudy / full of bubbles. How do I get water-clear results?
Clear casting is the least forgiving job, with these three different defects, there are three different causes:
- Cloudiness → usually moisture or incomplete mixing. Keep everything dry (clear urethanes react with humidity), mix thoroughly, and avoid wet molds or damp colorants.
- Bubbles → cure under pressure (a pressure pot is essentially required for flawless clarity), and pour slowly in a thin stream.
- Yellowing → most clear resins amber over time or under UV. For maximum long-term clarity and UV resistance, choose a water-clear grade rated for it or add a UV stabilizer like Sun Devil if the part will see sunlight.
Thickness & heat: Thick clear pours build up more exotherm, which can yellow or crack them. For deep/thick castings, pour in layers or use a resin formulated for thick sections, and let each layer cool before the next.
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Related guides: Bubbles, Voids and Degassing · Humidity