When we talk about coffee extraction, we usually talk about grind size, water temperature, brew ratio and agitation.
But there is another variable sitting underneath all of them:
the water itself.
Water is the medium through which coffee compounds move from the grounds into the cup. But whether the minerals dissolved in that water directly change extraction is a much more interesting — and less settled — question than coffee-water charts sometimes suggest.
And this is where the science gets interesting.
The classic idea: minerals help extract coffee
One of the most influential papers in coffee-water science came from Christopher Hendon, Lesley Colonna-Dashwood and Maxwell Colonna-Dashwood in 2014.
Their work examined how calcium, magnesium and sodium ions could interact with compounds found in coffee.
The results suggested that dissolved cations can influence the thermodynamics of coffee-compound extraction, with magnesium showing particularly strong interactions in their model.
This became an important foundation for how specialty coffee thinks about mineralised brewing water.
But turning that into a simple rule such as "more magnesium means more extraction" is too simplistic.
Then came the challenge
More recent experimental work has challenged how directly calcium and magnesium affect extraction at realistic drinking-water concentrations.
One 2024 study investigated calcium and magnesium chloride experimentally and found limited variation in several measured organic acids at typical concentrations.
The researchers suggested that some sensory differences associated with mineralised water may arise from interactions between ions and coffee compounds after extraction, rather than simply from extracting more of those compounds.
That challenges the simple idea that:
More magnesium automatically means more extraction.
So who is right?
It would be wrong to say that the earlier work was simply wrong.
It would also be wrong to say that minerals definitely increase extraction in every practical brewing situation.
The studies ask different questions and use different methods.
The important conclusion is:
Water clearly matters.
Exactly how its minerals matter is still being worked out.
And that is a much more interesting place to start.
Extraction isn't the whole story
Imagine two cups containing similar amounts of extracted compounds.
They don't necessarily have to taste identical.
The dissolved minerals may influence the chemical environment of the finished beverage, including interactions between ions and compounds already present in solution.
So when a brewer says:
"This water makes my coffee taste sweeter."
that does not automatically mean:
"This water extracted more sweetness."
Those are different claims.
What about bicarbonate?
Bicarbonate brings another layer into the conversation.
Unlike calcium and magnesium, bicarbonate is closely associated with alkalinity and buffering.
Coffee contains acids.
Alkalinity influences the water's capacity to neutralise acids, which can change how acidity is expressed in the final cup.
This means water can influence the perception of acidity without us needing to claim that it simply extracts more or less coffee.
Why TDS isn't enough
Two waters can have similar TDS while containing very different proportions of calcium, magnesium, sodium, bicarbonate and other ions.
The number tells us something about how much dissolved material is present.
It does not tell us exactly what that material is doing.
Water as an experimental variable
This is where The Water Artist philosophy begins.
We don't want to pretend coffee-water science has reached its final answer.
We want to use what we know, acknowledge what we don't, and experiment with the variable we can control:
the water.
Change the mineral composition.
Keep the coffee, grinder, ratio, temperature and technique constant.
Taste the difference.
Then change one variable again.
That turns water from a fixed ingredient into an experimental tool.
The Water Artist
We don't sell certainty where the science is still evolving.
We explore.
Water is the canvas.
You're the artist.