How to Fix Bubbles in Coloured Polyurethane Resin

Q: How to Remove Bubbles Before Curing

Tapping the mould: Gently tap or shake the mould after pouring to help trapped bubbles rise to the surface and pop. Applying gentle warmth: Use a hairdryer or warm (not hot) water bath briefly under the mould base to help bubbles escape. Take care not to overheat, which may affect curing. Act quickly: Most polyurethane resins, such as the IWhite Polyurethane Casting Resin , cure rapidly (around 30 minutes), so bubble removal needs to be carried out immediately after mixing and pouring.

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What to Do If My Coloured Resin Has Bubbles?

Noticing bubbles in your coloured polyurethane resin cast can be frustrating, especially when aiming for a clear, smooth finish. Thankfully, there are simple techniques you can use to minimise or remove bubbles before your resin cures.

Why Do Bubbles Form in Coloured Resin?

Bubbles typically appear when air becomes trapped during the mixing or pouring process. Colouring agents mixed into liquid resin can also introduce additional air, making bubbles more likely. While small bubbles are common, they can obscure detail or affect the clarity of your finished piece if not addressed promptly.

How to Remove Bubbles Before Curing

Tapping the mould: Gently tap or shake the mould after pouring to help trapped bubbles rise to the surface and pop.
Applying gentle warmth: Use a hairdryer or warm (not hot) water bath briefly under the mould base to help bubbles escape. Take care not to overheat, which may affect curing.
Act quickly: Most polyurethane resins, such as the IWhite Polyurethane Casting Resin, cure rapidly (around 30 minutes), so bubble removal needs to be carried out immediately after mixing and pouring.

Practical Tips to Avoid Bubbles

Mix slowly to minimise adding air.
Pre-warm resin and moulds to reduce viscosity for easier bubble release.
Pour in a thin stream, close to the mould’s surface, for gentler fills.

For doming and flexible surface projects, consider products like Be Flex Transparent Polyurethane Doming Resin, which is formulated to achieve a bubble-free glossy finish.

When Does Bubble Removal Matter Most?

Bubble reduction is especially important for intricate designs or transparent pieces, where clarity and fine details define the quality of your work. Prioritise careful mixing and bubble release steps for best results in these cases.

Related guides

How To Colour Polyurethane Resin

Managing bubbles is a key step towards professional-looking resin casts. For more tips and guidance on working with tinted resins, visit our main guide on how to colour polyurethane resin.