Input lever
Water Chemistry
Detail panel
Water source
The base water used for brewing.
AeroPress Wheel Variable
Hardness
Water Chemistry · Input lever
The calcium and magnesium load that drives brewing hardness.
Input lever
Water Chemistry
Wheel face
Measurement-friendly
Official standard
Technical science
Competition practice
Definition
Hardness mainly reflects calcium and magnesium ions that influence extraction behavior, structure, and mouthfeel.
Why It Matters
Hardness is one of the strongest water controls affecting extraction strength and cup structure.
Measurement Options
Water report
Recipe calculation
Test kit
Page Context
Hardness is part of the Brew Supply AeroPress Wheel and helps brewers describe the calcium and magnesium load that drives brewing hardness.
Related variables
Input lever
Water Chemistry
Wheel face
Water recipe
A deliberate mineral recipe added to low-mineral water.
Input lever
Water Chemistry
Wheel face
Water TDS
The total dissolved solids of the brew water.
Input lever
Water Chemistry
Wheel face
Alkalinity
The water’s buffering capacity, often driven by bicarbonate.
Input lever
Water Chemistry
Advanced detail
Calcium
A hardness ion commonly present in brewing water.
Input lever
Water Chemistry
Advanced detail
Magnesium
A hardness ion commonly used in custom brew-water recipes.
Affected outcomes
Measured metric
Cup Outcome
Wheel face
Beverage TDS
Measured total dissolved solids in the served beverage.
Calculated metric
Cup Outcome
Wheel face
Extraction Yield
Calculated percentage of coffee mass extracted.
Measured metric
Cup Outcome
Wheel face
Beverage Yield
The liquid beverage mass collected or served.
Cup outcome
Cup Outcome
Wheel face
Aroma
The smell of the brewed coffee.