1. Overview & Physics
Solvent Chemistry of Water
Coffee is 98% water. The minerals dissolved in your brewing water act as complex binding agents. Magnesium ions (Mg2+) form strong coordinates with oxygen-rich flavor compounds, pulling out bright fruits and sweetness. Calcium (Ca2+) binds to heavy organic acids, emphasizing creamy body. However, high calcium leads to scale, requiring balanced ppm control.
The Ideal Water Recipe
Target a total hardness of 70-120 ppm, with a 2:1 ratio of Magnesium to Calcium, and a low carbonate hardness (buffer) of 40 ppm.
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 magnesium extract better coffee flavor?
Magnesium (Mg2+) ions have strong chemical bonds that easily bind with volatile oxygen compounds in coffee, pulling sweet flavors into the liquid.
Does calcium scale the espresso boiler?
Yes, high calcium (Ca2+) concentrations cause calcium carbonate scale buildup inside copper boilers under high heat.
