You mix glow powder into your resin, pour a beautiful piece, and when you turn the lights off, all the glow is in a thin layer at the bottom. It is one of the most common glow resin problems - and it is easy to fix once you know why it happens.
Why Glow Pigment Sinks in Resin
Glow in the dark pigment does not dissolve. It is made of tiny strontium aluminate crystals that hang in the resin, and those crystals are around three times heavier than the resin around them. While the resin is still runny, gravity slowly pulls them down. Four things decide how fast that happens:
- How thin the resin is. Thin, watery resin lets pigment sink fast. Thicker resin holds it in place.
- How long the resin takes to cure. Slow-curing deep-pour resins stay runny for hours, giving pigment lots of time to sink.
- Particle size. Bigger, heavier crystals sink faster than fine ones.
- Temperature. Warm resin is thinner, so pigment sinks faster in a warm room.
8 Ways to Stop Glow Powder Settling
1. Wait before you pour
This is the most effective fix. Right after mixing, resin is at its thinnest. Mix in your pigment, then let the batch sit until it thickens slightly - it should flow like warm honey rather than water - give it a final gentle stir and pour. Test with a small cup first, because the right moment depends on your resin and room temperature.
2. Use a thicker resin
Coating and jewellery resins are thicker and cure faster than deep-pour casting resins, so pigment stays where you put it. Save deep-pour resin for projects where you are happy for the glow to collect at the base.
3. Choose a finer particle size
Our glow pigments come in two sizes. The 0–30 µm size tends to stay suspended longer than 65–90 µm. The larger size is the one we recommend for maximum brightness, so it is a trade-off: fine for an even glow, coarse for maximum brightness.
4. Pour in thin layers
Instead of one deep pour, pour several thinner layers and let each one start to gel before adding the next. Each layer keeps its own pigment, so the glow ends up spread through the whole piece.
5. Stir again during early curing
For small pieces, gently stir or tilt the mould once or twice during the first stage of curing to lift the pigment back up. Stop as soon as the resin starts to gel, or you will leave marks.
6. Work in a cooler room
If your room is very warm, the resin stays thinner and the pigment sinks faster. Working at normal room temperature, rather than next to a heater, helps.
7. Use a thickening additive (advanced)
Some resin artists add a small amount of a thixotropic additive such as fumed silica to thicken the resin so pigment stays suspended. If you try this, follow the additive maker's instructions and test first, as it can make clear resin slightly hazy.
8. Dust the mould before pouring
If you want the glow on the visible face of the piece, sprinkle a thin, even layer of glow powder into the empty mould first, then pour your resin over it. The glow ends up concentrated exactly where you will see it, and settling no longer matters.
Is Settled Glow Always a Bad Thing?
Not at all. Settled pigment creates a concentrated glow layer that can look amazing - a glowing "floor" in an ocean scene, a bright base under a clear dome, or a glowing edge on a coaster. Some artists let it settle on purpose. The key is controlling it, not fighting it every time.
Other Reasons Your Glow Resin Looks Patchy
- Clumps: pigment was added too fast, or the powder was damp. Pre-mix it into a little resin first, and keep the bag sealed between uses.
- Weak glow overall: not enough pigment. Aim for pigment to be 20–30% of the total mix by weight, if your resin allows it.
- Cloudy resin: moisture in the powder or too many bubbles. Keep pigment sealed and dry, and stir slowly.
For the full process from start to finish, see our guide on how to make glow in the dark resin. And if you are painting rather than pouring, our article on 7 mistakes that kill the glow covers settling in paint.
Frequently Asked Questions
Why does my glow powder sink to the bottom of resin? Glow crystals are heavier than resin and do not dissolve, so they sink while the resin is still runny. Thin, slow-curing resin and larger particles make it happen faster.
How do I keep glow powder suspended in resin? Let the resin thicken slightly before pouring, use a thicker coating resin, choose the 0–30 µm particle size, pour in thin layers, and avoid adding more pigment than you need - overloading makes settling worse.
Does fluorescent pigment sink in resin too? It can, but usually more slowly - fluorescent powders are only 2–5 µm. Resin thickness and curing time matter for both.
Does settled glow pigment still glow? Yes - it glows just as brightly, only concentrated in one layer instead of spread through the piece.
Can I fix resin that has already cured with settled pigment? You cannot move the pigment once cured, but you can pour a new glow layer on top to spread the glow higher in the piece.
Written by the GlowThatWows team - specialists in strontium aluminate glow in the dark pigments and paints.
