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Water Chemistry
Detail panel
Water source
The base water used for brewing.
Different sources can have very different mineral content, cleanliness, and flavor impact.
AeroPress Wheel Domain
Water Chemistry
Domain 02 · 11 controls · 6 states, metrics & outcomes
Water Chemistry describes the mineral and chemical composition of the brewing water and the solvent environment it creates.
Domain 02
11 controls · 6 states, metrics & outcomes
Water Chemistry is one of the ten primary AeroPress Wheel domains and gives brewers a structured way to control water decisions.
Why It Matters
Water changes extraction efficiency, buffering, clarity, sweetness, acidity perception, and mouthfeel. It is one of the strongest controllable variables in advanced brewing.
Use It To
Lock the water before drawing taste conclusions from grind or agitation. Different waters can make the same recipe behave like a different brew entirely.
How To Read This Domain
Start with the controls in this domain, then read the states, metrics, and outcomes they tend to influence. In practice that keeps brew notes honest: it separates the levers a brewer chose from the signals the brewer observed afterward.
That distinction matters during dial-in because recipe language often collapses cause and effect into one sentence. This domain page is designed to keep them apart so a later cup change can be traced back to a clearer brewing decision instead of a vague impression.
Read the page from top to bottom when you want the broad logic, then use the related variables and linked domains when you need to branch into a narrower troubleshooting path.
Controls
Input lever
Water Chemistry
Wheel face
Water recipe
A deliberate mineral recipe added to low-mineral water.
A recipe lets you tune hardness, alkalinity, and ion balance directly rather than inheriting them from the source water.
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Water Chemistry
Wheel face
Water TDS
The total dissolved solids of the brew water.
Water TDS is useful context, but two waters with the same TDS can extract and taste very differently.
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Water Chemistry
Wheel face
Hardness
The calcium and magnesium load that drives brewing hardness.
Hardness is one of the strongest water controls affecting extraction strength and cup structure.
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Water Chemistry
Wheel face
Alkalinity
The water’s buffering capacity, often driven by bicarbonate.
High alkalinity can flatten acidity and reduce clarity, while lower alkalinity can preserve brightness.
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Water Chemistry
Advanced detail
Calcium
A hardness ion commonly present in brewing water.
Calcium contributes to extraction structure and can shape the feel of the water differently from magnesium.
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Water Chemistry
Advanced detail
Magnesium
A hardness ion commonly used in custom brew-water recipes.
Many brewers associate magnesium-heavy waters with stronger extraction intensity and pronounced flavor expression.
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Water Chemistry
Advanced detail
Sodium
A mineral ion that can change taste and water balance.
It is usually a secondary advanced water variable, but it still contributes to the whole water profile.
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Water Chemistry
Advanced detail
Bicarbonate
The main alkalinity contributor in many brew-water recipes.
Adjusting bicarbonate changes how vivid or muted acidity feels in the cup.
Input lever
Water Chemistry
Detail panel
pH
The acidity or basicity of the water.
pH can still indicate extreme water conditions or recipe mistakes, especially when building custom waters.
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Water Chemistry
Detail panel
Chlorine / chloramine removal
Filtration or treatment that removes disinfectants from water.
Water off-flavors contaminate every brew, so water cleanliness is foundational.
States, metrics & outcomes
Process state
Water Chemistry
Wheel face
Buffer capacity
How strongly the water resists pH change.
Strong buffering can soften or mute acidity and change how balance presents in the final cup.
Process state
Water Chemistry
Advanced detail
Mineral balance
The relationship between hardness, alkalinity, and specific ions.
Two waters with the same TDS can taste very different because their mineral balance differs.
Direct observation
Water Chemistry
Wheel face
Acidity modulation
How the water changes perceived acidity.
This is one of the fastest ways water changes a competition coffee’s presentation without changing the recipe mechanics.
Direct observation
Water Chemistry
Detail panel
Flavor clarity
How distinctly the coffee’s flavors are separated.
Water can clarify a coffee’s profile or make it taste muddy even when extraction is similar.
Process state
Water Chemistry
Detail panel
Extraction efficiency
How effectively the water extracts soluble material.
Water chemistry changes how much grind, heat, and agitation are needed to reach a target result.
Direct observation
Water Chemistry
Wheel face
Water cleanliness
The absence of off-flavors from the water itself.
Clean water is the baseline condition that makes every other recipe variable meaningful.
Common Mistakes
- Using water TDS as if it explains everything about water behavior.
- Changing bottled water or remineralization without recording it.
- Talking about pH alone while ignoring buffering capacity.
Competition Notes
- Competition brewers often tune alkalinity and magnesium separately to preserve acidity or add structure.
- Water cleanliness is non-negotiable; off-flavors from water contaminate every other decision.
Recipe Language
125 ppm remineralized water at 84°C.
Distilled water plus minerals to 87 ppm.
Domain Context
Water Chemistry is one of the ten primary AeroPress Wheel domains and gives brewers a structured way to control water decisions.
What To Measure
- Track source, hardness, alkalinity, and total recipe if you remineralize.
- Separate water TDS from hardness and alkalinity in your notes.
- Log chlorine/chloramine removal as a yes/no setup variable when relevant.
Related Domains
Related Variables