"Magnesium extracts more coffee."
It is one of the most repeated statements in specialty coffee water.
But the real answer is more complicated.
Magnesium clearly matters in coffee-water chemistry.
The question is whether increasing magnesium in realistic brewing water necessarily produces more extraction.
That is a different question.
Where did the idea come from?
The influential 2014 work by Hendon, Colonna-Dashwood and Colonna-Dashwood investigated interactions between coffee compounds and dissolved cations.
Their computational chemistry work suggested that magnesium could interact strongly with certain compounds found in coffee.
This helped establish a mechanistic basis for why mineralised water could influence coffee brewing.
It also helped popularise magnesium-forward water recipes.
But molecular interaction isn't the same as practical extraction
A molecule can interact strongly with another molecule in a model.
That doesn't automatically mean increasing its concentration in a real coffee brew will produce a large increase in extraction.
Real brewing involves:
temperature
concentration
time
diffusion
grind distribution
water composition
coffee matrix
and many other variables.
The system is complicated.
What did newer experiments find?
More recent experimental work has questioned how strongly realistic concentrations of calcium and magnesium change the extraction of measured organic acids.
In a 2024 study, calcium and magnesium chloride were added at concentrations relevant to drinking water and coffee brewing.
The researchers observed relatively limited changes in measured acid concentrations at those typical levels.
At substantially higher concentrations, differences became more apparent.
That is an important result.
It suggests we should be cautious about turning the Hendon model into a simple brewing rule.
So does magnesium do nothing?
No.
That conclusion would go too far.
Water composition can influence the resulting beverage.
But the mechanism may not simply be:
magnesium enters water
→ magnesium extracts more compounds
→ coffee tastes better.
Minerals may influence the chemical environment during extraction and may also interact with compounds after they have entered solution.
Extraction and perception are different questions
Suppose two coffees contain similar amounts of extracted compounds.
They can still taste different.
Why?
Because sensory perception depends on much more than total concentration.
Interactions between dissolved compounds can influence what we perceive.
That means:
"this water tastes sweeter"
does not necessarily mean:
"this water extracted more sweetness."
Those statements are not equivalent.
What about APAX?
APAX's sensory work provides another perspective.
Their work associates different ions with sensory directions in coffee.
Magnesium-rich profiles have been associated with characteristics such as brightness, fruitiness and sweetness.
These observations are valuable for brewers.
But sensory association is not automatically proof of a molecular extraction mechanism.
It is better to say:
"this profile was associated with this sensory direction"
rather than:
"this ion causes this flavour."
The practical lesson
If you are experimenting with magnesium, don't simply increase it until the coffee tastes better.
Instead, compare controlled profiles.
For example:
Water A:
lower magnesium
Water B:
higher magnesium
Keep everything else constant.
Then taste blind if possible.
Ask:
What changed?
Not:
Did magnesium extract more?
The sensory experiment should come before the conclusion.
Magnesium is one variable
Coffee water contains more than magnesium.
If you add MgCl₂, you also add chloride.
If you add MgSO₄, you also add sulfate.
Changing magnesium therefore changes the overall ionic composition.
That makes isolated claims about "magnesium" difficult unless the rest of the system is controlled carefully.
So, does magnesium extract more?
The most responsible answer is:
**The evidence does not justify treating "more magnesium = more extraction" as a universal brewing law.**
The original mechanistic work provides an important foundation.
More recent experimental research suggests the practical relationship is more complicated.
Sensory work shows that mineral composition can be associated with meaningful differences in the cup.
The exact mechanisms remain an interesting area of research.
The Water Artist approach
We don't need to choose between:
"magnesium matters"
and:
"magnesium doesn't matter."
The more useful position is:
magnesium is an important variable.
Its effect depends on the complete water composition and brewing context.
Test it.
Measure it.
Taste it.
Then decide what it does for your coffee.
The Water Artist
Don't turn a hypothesis into a rule.
Use the water as an experiment.
Water is the canvas.
You're the artist.