Part of the Ice and Dilution school. Class 2 of 6.
The capability: you can tell what the ice will do to a drink before you build it.
Prerequisites: Module 9.
The practice
At eleven at night, build the same stirred drink twice — once from the service well, once from fresh machine ice, same count. Taste them together.
Then repeat at six in the evening and note whether the difference is smaller.
Then handle ice deliberately. Scoop it and listen — fresh ice rings, tired ice thuds, and that is a free indicator available every time a glass is filled.
And run the ice quantity test: the same highball with a full glass of ice and half a glass, tasted at five minutes, per Module 9 — because more ice makes a colder, less diluted drink and the intuition runs backward.
The reference
Fresh machine ice. That is the standard and the well is the variable.
What you are building
The recognition that ice is an ingredient with a specification — and the only ingredient behind the bar that changes continuously across a shift while nobody watches it.
And the two opposite failures, which is the part that retires the count for good: tired well ice over-dilutes at a given count, and exceptionally cold hard ice straight from a cycled machine under-dilutes at the same count, because it has to warm to the melting point before any phase change begins.
A count is wrong in both directions depending on conditions.
Verification and boundary
The eleven o'clock side-by-side, tasted blind.
Boundary: ice is a food product and machine sanitation and handling are governed by the local health authority.