Brewing control chart

Two-dimensional chart (TDS on y-axis, extraction yield on x-axis) defining the ideal zone of well-extracted coffee (TDS 1.15-1.35%, EY 18-22%). Developed by E.E. Lockhart (MIT, 1950s), standardised by SCAA. Diagnostic tool to identify under-extraction (low EY) or over-extraction (high EY).