1. Overview & Physics
Frictional Thermodynamics
Grinding coffee generates massive friction. Steel burrs act as heat sinks. In busy home cafes, consecutive grinding can raise burr temperatures past 40째C. Warm burrs pre-heat the dry coffee grounds, altering the extraction rate and causing consecutive espresso shots to run faster and taste bitter.
Grinder Management
Purge a few grams of coffee if your grinder has sat idle after heavy use, or choose flat ceramic burrs, which conduct heat slower than steel.
2. Practical Calibrations
Managing this requires measuring indicators in real time. Adjust grind size, water dynamics, and flow parameters incrementally. Change only one variable at a time to ensure clean results and isolate target parameters.
Barista Action Checklist
- Weigh dry grounds dry dose exactly to 0.1g.
- Calibrate water temperature using PID sensors.
- Target correct brew ratios (e.g. 1:15 for filter, 1:2 for espresso).
- Swirl or stir to ensure even saturation during extraction.
- Record extraction time and evaluate flavor notes subjectively.
Frequently Asked Questions
Why does grinder burr heat matter?
Burr friction heats the coffee grounds, vaporizing volatile aroma oils before brewing starts and accelerating extraction rates.
How do I prevent burr heating?
For home use, single-dosing grinders with low RPM motors minimize friction heat buildup compared to commercial grinders.
