If you've ever wondered what determines the brewing characteristics of a water, this post is for you. We'll cover the ionic mineral compounds, the individual ions, the relevant ion ratios, TDS, and what it all means in a brewing context.
There are many ionic mineral compounds that can be used to add mineral content to water, all of which are naturally occurring in mineral water. Listed below are the most relevant mineral compounds used over the years of developing Empirical Water:
- Sodium bicarbonate
- Sodium chloride
- Sodium sulfate
- Potassium bicarbonate
- Potassium chloride
- Potassium sulfate
- Calcium carbonate
- Calcium chloride
- Calcium sulfate
- Magnesium carbonate
- Magnesium chloride
- Magnesium sulfate
Notice some trends. First off, sodium, potassium, calcium and magnesium always appear first, because they are the positively charged cations. Bicarbonate, carbonate, chloride and sulfate appear second, because they are the negatively charged anions.
When ionic mineral compounds dissolve in water, they dissociate into positively charged cations and negatively charged anions. For example, the ionic compound calcium chloride (CaCl2) dissociates into the positively charged calcium cation, Ca2+, and two negatively charged chloride anions, Cl-.
The following ions occur in water as a result of the above mineral compounds dissociating to dissolve.
- Calcium - Primary flavor extractor, focused on sweetness.
- Magnesium - Primary flavor extractor, focused on warmth.
- Sulfate - Increases flavor definition.
- Chloride - Reduces flavor definition.
- Sodium - Texture, warmth and sweetness.
- Potassium - Saps sweetness even in miniscule amounts, and tastes bitter and metallic. Empirical Water contains no potassium.
- Bicarbonate - Acts as a buffer to reduce intensity/acidity. Generally reduces top notes, making everything taste "bassy" in high amounts.
Note: Once an ionic mineral compound dissolves, the dissociated ions act independently to affect extraction.
To think about water effectively in a brewing context, it's helpful to group some of the ions together, with regard to how they affect extraction.
Calcium and magnesium get grouped together, as they are both primary flavor extractors, but leaning in different directions: Sweetness vs warmth. A well-balanced water includes both the sweetness of calcium and the warmth/savory side of magnesium.
The flavor/textural definition of sulfate is countered by the smoothing quality of chloride. In balanced amounts, you get plenty of definition without harshness or off-notes.
Then, we have the hardness to alkalinity ratio - Which basically just tells us how intensely the water is going to interact with the coffee. Ions that contribute to hardness include calcium and magnesium, while bicarbonate makes up the alkalinity. The higher the ratio of hardness to alkalinity, the higher the intensity.
So where does the key ingredient, calcium carbonate fit into all this?
By swapping out some calcium chloride/sulfate for calcium carbonate, we can maintain calcium content while reducing chloride and sulfate. Empirical Water gets about half of its hardness from calcium carbonate.
The result? It cleans up the flavor profile beautifully, while directly expressing the very core of the flavor. It gets you right to the elements in coffee you're looking for: sweetness, clarity, aromatics, texture and aftertaste, without harshness or off-notes. It makes your brewing parameters more forgiving, so you're not constantly chasing that dialed in brew. Stuff just comes out tasting good without thinking too much about it.
Total Dissolved Solids, expressed as mg/L or ppm. It's simply the total amount of mineral per unit of water. TDS matters, but not in the way most people think. It's far less important than composition. A huge range of TDS can work for brewing good coffee; what matters is how the composition is balanced to perform well at that TDS. Higher TDS waters have more texture, but it's tough to generalize beyond that.