Pigment loading

Pigment doesn't take part in the cure. It just sits in the resin. A little gives you colour. Too much dilutes the chemistry, and you get soft spots, a tacky surface, or a brittle part. Working in percent of mix weight lets you repeat a colour exactly from a 50 g test cup to a 5 kg pour, and it keeps you below the load where the cure starts to suffer.

Notes

1. The typical ranges come from common practice, not from any standard: mica powder 1–3%, liquid dye or epoxy colourant 0.1–2%, alcohol ink 0.1–1%. Pigment makers disagree, and some rate mica up to around 6%. Your pigment's own guidance comes first. Above 5% you'll get a hard warning whatever the pigment. Alcohol ink brings solvent into the mix, which is a common cause of soft cures when it's used heavily.
2. "3% pigment" can mean two things: 3% of the resin + hardener weight, with pigment added on top (the common convention), or 3% of the finished mix. At normal loads the difference is small, but it's real. Both figures are shown whichever you pick.
3. Mixed density depends on your product and ratio. For example, 1:1 by volume at SG 1.15 and 0.95 gives 1.05 g/mL. For precise colour matching, weigh the batch instead.
4. Add pigment on top of the full A + B mix. Never hold back hardener or resin to make room for it.