Batch-to-batch colour drift — what can the formula actually do?

Fix the grade, control incoming batches, and build a little tolerance into pale shades. The formula cannot eliminate it.

Pigments are mineral or synthetic and natural variation exists — inorganics especially, where the ore source matters. Three layers of control: hold one grade and one supplier instead of switching on price; require a coloristic value or ΔE on the COA, which most suppliers can provide; and inspect on receipt against a retained standard, rejecting or re-matching outside the agreed window.

Inside the formula, pale shades are the sensitive ones. Keeping a small headroom in the pigment loading lets you trim rather than reformulate. Deep shades absorb more drift but still need a fixed standard.

The habit that beats data: retain a drawdown panel from every batch — same base, same process — and compare panels on the next delivery. It is faster than reconciling L/a/b across suppliers.

If the same SKU is made at more than one site, tighten the standard and single-source the pigment. Two sites plus two pigment sources is where drift becomes unfixable.