Acrylic dry shift: how to mix for the dried color

Why the wet swatch lies

Wet acrylic is pigment suspended in a milky binder. The binder is white while wet and clear once cured, so the wet film scatters more light than the dry film ever will. Mix to a perfect wet match and you have effectively mixed a colour that is one step too light, because the binder was doing part of the lightening for you. Twenty minutes later the binder clears and the mix drops.

• Judge the mix on a dry swatch, on the same ground you are painting on.
• Keep a scrap of the actual substrate on the bench, not a random offcut of paper.
• If you must judge wet, aim a little lighter than the target on purpose.

How big the shift actually is

Chromilla's model applies a signed value shift of -0.10 for acrylic (a 10 per cent drop toward black), then nudges red up by 3 and blue down by 2 to account for the binder warming as it cures. Oil is treated as -0.01, which is inside the neutral band, so oil is reported as drying true to colour. Watercolour carries -0.08 in the model, with a small cool nudge. Those are the constants the solver scores against, not a rule of thumb.

• #8F9674

  Sage green, wet versus dry

  • Wet mix
  • Dried film

  Same paint, twenty minutes apart. The dried value is what your viewer sees.

Worked example: sage green in acrylic

Target #9CA783. Chromilla's acrylic solve returns Titanium White 68 per cent, Ultramarine Blue 18 per cent, Burnt Sienna 14 per cent, landing at #9CA582 once dry, a delta E of 0.9 against the target and a 98 per cent match. Mix that ratio and the wet paint on your knife will look noticeably lighter and greener than the chip. That is correct, not a mistake: the wet reading of that same film is around #ADB891 before the binder clears.

• Do not correct the wet mix toward the target. You will overshoot dark.
• Swatch, wait for the sheen to go matte, then compare.

What Chromilla cannot do here

The 10 per cent figure is a medium-level average. Heavy body and fluid ranges from the same brand do not dry identically, and a very thin scumble over a white ground shifts less than a thick opaque pass. Where a brand publishes its own drying shift, Chromilla uses that instead of the medium default. Where it does not, you are getting the average, and a heavily thinned acrylic will beat the model.