Writing a formula you can repeat

A formula that lives in your head is not a formula, it is a habit. The difference shows up the first time somebody else makes the blend, or the first time you make it after a three month gap.

What a formula has to contain

More than the ingredient list. A blend that comes out the same twice needs the components and their proportions, the grind of each, the order of addition, the mixing time and speed, the batch weight it was developed at, and the supplier and specification of anything where those matter.

Most written formulas contain the first two and produce inconsistent results for the absence of the other five.

Percentages and a batch weight

Components as percentages of total weight. Batch weight as a separate figure. Actual quantities derived from the two rather than written down, so that scaling cannot go partly wrong.

Weigh everything, including the things it seems reasonable to measure by volume. A teaspoon of a fine powder and a teaspoon of a leaf are not comparable quantities of anything.

The parts nobody writes down

Which supplier, when the character of a component varies by origin. What the grind screen was. Whether a component was toasted, and for how long. Which order things went in, when a small-quantity component has to be pre-diluted to distribute.

Those are the variables that change silently, usually when something is out of stock and a substitution seems minor.

Version it

Date every formula and never overwrite one. When a blend changes, write a new version and keep the old, because the question that eventually arises is what was in the batch a customer bought last year and the honest answer has to be findable.

Pair the version with the retained sample from the batch and the record becomes something you can actually taste rather than only read.

References