Why your resin has bubbles (and which ones matter)
Six causes, ranked by how often they're actually the problem. Most of the time it isn't your mixing.
Bubbles are the number one message in our inbox, and roughly seventy percent of the time the cause is not the one people assume. Here they are, ordered by how often they actually turn out to be the culprit.
1. The room was too cold
Cold resin is thick resin, and thick resin cannot release air. Below about 22°C, viscosity roughly doubles and bubbles that would have risen in ninety seconds simply never make it to the surface. This is the cause more often than everything else combined.
2. Unsealed porous substrate
Wood, plaster, concrete and MDF all hold air. Resin flowing over them warms the trapped air, which expands and outgasses upward — producing a fine bubble haze that tracks the grain. One thin seal coat, cured to tack, eliminates it.
3. Mixing too fast
A drill mixer at speed whips air in faster than the resin can shed it. Hand-stir, slowly, for three minutes. You are not trying to aerate a batter.
4. Not doing the double-cup
Unmixed resin clings to the cup wall and base corner. Transferring to a second clean cup and mixing one more minute is the single most reliable way to avoid both bubbles and soft spots.
5. Pouring too close to the surface
Counter-intuitively, pouring from height helps: the thin stream shears and the bubbles break on the way down. Pouring from two centimetres just folds air in.
6. It's actually fine
Micro-bubbles below about 0.3mm, distributed evenly through a deep pour, are visually invisible at arm's length and are present in most gallery pieces. Not every bubble is a defect. Learn which ones you'd actually notice from where the piece will be seen.
Warm the resin, seal the wood, stir slow, double-cup. That's ninety percent of it.
Put it into practice
Everything in this article, on one bench.
Our starter benches ship with enough material for two attempts and a printed pour card — so the technique above has somewhere to land.