Epoxy pigment calculator

Colour is measured as a percentage of the mixed resin (resin and hardener already stirred together). If your resin’s data sheet (TDS) gives a maximum, enter it too — going over it can stop the resin curing properly.

How much pigment to put in resin

Pigment amounts are given as a percentage of the resin, usually by weight. Two percent means 2 g of colour for every 100 g of mixed resin — Part A and Part B already stirred together, because that is what you colour. So the only real work is knowing how much your batch weighs. If you weighed it, you already know. If you measured it in cups, multiply the volume by the resin’s density: most clear epoxies weigh about 1.05–1.2 g per ml, and the calculator uses 1.1 unless you change it under More options.

resin weight = volume × density (≈ 1.1 g/ml)
pigment = resin weight × loading %
if the % is of the finished mix: pigment = resin × p ÷ (1 − p)

A worked example with the default numbers: a 16 fl oz batch is about 473 ml, which at 1.1 g/ml weighs about 521 g. At 2% that is about 10.4 g of pigment — a level scoop of mica powder, not a jarful. The table above shows the same batch from half a percent up to 6%.

How much is too much?

Every resin has a limit, because pigment isn’t part of the chemistry. It dilutes the resin and hardener, and past a point the mix can cure soft, stay tacky or end up weaker. The figures published by makers are modest: WEST SYSTEM’s Epoxyworks suggests about 5% by weight for its pigments and notes that pigment weakens the cured epoxy to some degree; ArtResin says not to add more than 6% of the mixed resin’s volume in colourant. Your resin or pigment may say something different — the data sheet wins. If a colour isn’t strong enough at the limit, add another coloured coat rather than more powder; thin films of coloured epoxy often need a few coats to look solid.

By weight, by volume, and why there are no teaspoons of powder

Powders and pastes are dosed by weight. A teaspoon is a volume, and a spoonful of light, fluffy mica weighs a fraction of a spoonful of a dense white pigment, so any “teaspoons of powder” figure would be a guess — the calculator doesn’t give one. Liquid tints are different: some labels give their limit by volume (ArtResin’s 6% is one), so the calculator also shows the same percentage as milliliters and as 5 ml measuring teaspoons. Drops aren’t shown, because the size of a drop depends on the bottle’s nozzle and the tint’s thickness.

Pros will recognise the default basis as parts per hundred resin (phr): pigment ÷ mixed resin. A few data sheets instead give a share of the finished mix, pigment ÷ (resin + pigment); switch The percentage is of under More options and the calculator divides by (1 − p). At 2% the difference is under a twentieth of a gram per 100 g, so it only matters near the limit.

Tips

• Mix Part A and Part B thoroughly first, then stir in the colour. Adding powder to one part alone throws off the ratio you measured.
• Weigh small amounts on a scale that reads to 0.1 g or 0.01 g. Kitchen scales that step in whole grams can’t measure 1–2 g accurately.
• Colouring a big pour? Colour a small test cup first and let it cure — colours often look different once the resin is hard.
• Several colours for one piece? Work out each cup separately: enter that cup’s batch size, not the whole kit.

To size the resin itself, start with the resin art calculator for a canvas or the coaster resin calculator for a set of molds — for example how much resin for 4 coasters — then colour each cup here.