Understanding Water Chemistry with First Touch: Hardness, Alkalinity, and pH

There is a substantial difference between saying that water is “important” and truly understanding how water works. At Meet Lab Coffee, we have long been working on the chemistry of brewing water, analyzing municipal waters from different cities and examining the relationship between water profiles and brewing outcomes. For this reason, it is hardly surprising to us that discussions around water have intensified among coffee professionals in recent years; in fact, this is simply a natural reflection of many of the issues we encounter in practice. Anyone seeking to understand the character of coffee eventually has to confront the behavior of water. No matter how extensively we discuss the bean, the roast, or the brew method, the invisible actor that often determines the final cup is the water itself. Filtration systems, mineral recipes, custom brewing waters, and laboratory analyses all remain central to our ongoing inquiry. Yet amidst all these discussions, one major problem persists: individual measurement.

When attempting to understand the character of water in the coffee brewing world, we often rely on a single number: TDS. However, a TDS measurement offers only limited information about water. TDS meters measure the total amount of dissolved solids in water. In other words, they estimate the total concentration of ions through electrical conductivity. What they do not reveal, however, is which minerals are actually present.

Put differently, two different waters with a TDS value of 120 ppm may have entirely different chemical characters. One may be dominated by calcium and magnesium, while the other may contain higher proportions of sodium or bicarbonate. A TDS meter cannot distinguish between these differences. Yet during dissolution and extraction, the identity and concentration of these minerals have a direct and profound impact on the taste of coffee. In short, for proper extraction, quality is just as essential as quantity. Therefore, while TDS remains an important reference point in coffee, it is not sufficient on its own to explain the true effect of water on brewing.

It is precisely at this point that what might be called a “dark zone” of coffee brewing emerges. Many coffee professionals believe they are measuring water, when in reality they are only observing the total amount of dissolved matter. The actual ions that govern extraction, the buffer capacity that moderates acidity, and the acidic or basic nature of water are often not measured directly, but instead inferred through assumptions.

At Meet Lab Coffee, our work on water led us to recognize this exact need. In order to understand the character of water in the brewing process, a clearer, more readable, and more direct method of measurement was necessary. Meet Lab First Touch was born from this idea. Its purpose was to enable brewers to evaluate the chemical character of the water they use through a simple yet scientifically grounded method, and to illuminate the invisible side of water. More importantly, it aimed to address the subject from the very beginning.

The First Touch kit focuses on measuring three fundamental parameters: total hardness, alkalinity, and pH. When these three parameters are evaluated together, the behavior of water in coffee extraction can be understood with considerable clarity.

Total hardness refers to the combined concentration of calcium (Ca²⁺) and magnesium (Mg²⁺) ions in water. These two minerals play a critical role in coffee extraction because many aromatic and flavor-active compounds in coffee dissolve more readily in the presence of these ions. For this reason, total hardness is often interpreted as the “solvent power” of water. In previous writings intended to make this concept more accessible, we described total hardness as the water’s “capacity to precipitate soap.” To make this more tangible, one may think of washing one’s hands with solid soap in mountainous areas or near natural springs and noticing that the soap does not lather properly. This is due to the hardness of the water: rather than producing foam, the water precipitates the soap. In this sense, hardness can indeed be understood as the water’s ability to collapse soap lather. When water with very low hardness is used, coffee often presents as weak, thin, and aromatically muted. Conversely, excessively hard water can make extraction overly aggressive, producing dominant and unbalanced flavor expressions in the cup.

In the First Touch kit, total hardness is measured according to the classical titration principle. A defined quantity of water is taken, and reagent is added drop by drop. After a certain number of drops, the color of the solution changes. This number of drops is then expressed in German degrees of hardness. For example, if the color changes on the sixth drop, this corresponds to 6 °dH. German hardness degree is a widely used unit in the international literature and can be converted into ppm. The conversion is approximately as follows: 1 °dH ≈ 17.8 ppm as CaCO₃. Accordingly, 6 °dH corresponds to roughly 106–107 ppm. In practical use, this value is typically rounded to 110 ppm. This falls almost exactly in the middle of the total hardness range of 50–175 ppm recommended by the Specialty Coffee Association and indicates a highly balanced water profile for coffee extraction.

Formally, the conversion may be expressed as follows:

°dH → ppm conversion

1 °dH × 17.8 = ppm as CaCO₃

Example calculation:

6 °dH × 17.8 ≈ 106.8 ppm ≈ 110 ppm

The second parameter that defines the character of water is alkalinity. In the coffee world, alkalinity is often misunderstood and confused with pH. In reality, alkalinity refers to the buffering capacity of water against acidity. In other words, it determines how much resistance the water will show when it encounters the organic acids present in coffee. In drinking water, alkalinity generally arises from bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) ions. For this reason, in coffee literature alkalinity is often referred to as carbonate hardness, or KH.

Alkalinity directly influences the perception of acidity in the cup. If alkalinity is too low, the coffee may be perceived as sharp, aggressive, and sometimes unpleasantly bright. In contrast, waters with high alkalinity may over-buffer the coffee’s acids, resulting in a flattened and muted cup. A balanced alkalinity level is therefore essential for achieving both liveliness and equilibrium in coffee.

In the First Touch kit, alkalinity is also measured through a drop-count titration method. During the test, reagent is added to the water and the color change is observed. For example, if the color changes on the sixth drop, this corresponds to 6 °dKH. German carbonate hardness degree is commonly approximated as 1 °dKH ≈ 10 ppm as CaCO₃. Therefore, 6 °dKH corresponds to approximately 60 ppm alkalinity. This value lies near the center of the 40–75 ppm alkalinity range recommended by the Specialty Coffee Association and indicates a water profile capable of producing balanced acidity perception in coffee.

Formally, the conversion may be expressed as follows:

°dKH → ppm conversion

1 °dKH × 10 = ppm as CaCO₃

Example calculation:

6 °dKH × 10 = 60 ppm alkalinity

The third parameter completing the chemical characterization of water is pH. pH indicates whether water is acidic or basic and is expressed on a scale from 0 to 14. For coffee brewing, a pH range close to neutral is generally preferred, because highly acidic or highly basic waters alter the chemistry of extraction. The Specialty Coffee Association recommends a pH range between 6.5 and 7.5. Waters within this range help aromatic compounds present themselves more clearly and support a balanced cup profile.

With the First Touch kit, pH is measured by adding reagent drops to the water and comparing the resulting color with the reference scale provided in the kit. For example, when the color comparison yields an approximate pH value of 7.1, the water can be understood to be very close to neutral. This represents a safe and balanced starting point for coffee brewing.

Formally, pH may be expressed as:

pH = −log[H⁺]

In practical terms, the recommended range for coffee brewing is:

6.5 ≤ pH ≤ 7.5

When these three parameters are considered together, the character of brewing water becomes much clearer. For example, a water with a total hardness of approximately 110 ppm, an alkalinity of approximately 60 ppm, and a pH of 7.1 falls within the limits recommended by the Specialty Coffee Association. Such a water both supports dissolution and keeps acidity in balance. As a result, it becomes possible to obtain a cup profile that is clean, balanced, and controlled.

This is precisely the core purpose of the Meet Lab First Touch kit: to make brewing water visible. Because brewing coffee is not only about understanding the bean, the roast profile, or the brewing equipment. Understanding the chemistry of water is equally essential. Once a barista or coffee enthusiast is able to measure the hardness, alkalinity, and pH of their water, they can approach the brewing process with far greater awareness.

In the coffee world, we often focus on equipment and technique. Yet one simple fact is frequently overlooked: we do not truly know the water we brew with. Meet Lab First Touch was designed to make this invisible field visible. The measurement process was simplified as much as possible, but in order to avoid confusion during use, an animated instructional clip explaining the full procedure in detail was prepared for each kit.

Once water is measured through these three fundamental parameters, what we gain is not merely a set of numbers, but a map describing the behavior of the water itself. Total hardness tells us about the dissolving capacity of the water, alkalinity reveals how it will buffer coffee acidity, and pH shows the broader chemical equilibrium of the medium. From this point onward, the brewer no longer proceeds in the dark; they understand where their water is strong and where it is limited.

At that stage, it becomes possible to move one step beyond analysis alone. Once the initial profile has been clearly identified, small mineral interventions can be applied in a controlled manner to guide extraction behavior. In other words, increasing the dissolving power of water, balancing acidity more effectively, or allowing aromas to emerge more distinctly becomes an intentional and informed intervention. Meet Lab First Touch is the first step in this process: knowing the water. After that stage of recognition, fine-tuning and enriching the water’s character according to the potential of the coffee forms the next phase. This naturally leads us to the Final Touch kit, with which many are already familiar. The reasons behind and methods of the Final Touch kit have already been discussed extensively in our blog. With First Touch, we make the initial contact with water through identification; with Final Touch, we make the enriching intervention. In this way, we gain the opportunity to carry our coffee brewing journey to a truly professional level, without leaving any dark points unresolved.

For professionals, with pleasure.