Hard or Soft: A Brewer's Dilemma

Making great beer really comes down to having great ingredients. Most homebrewers put considerable time and energy into finding the right grains, hops, and type of yeast to use, but often overlook one of the most important ingredients, water. Water chemistry can have a large impact on the final outcome of the desired beer style. It’s not so much the water but the minerals and their associated ions that affect appearance and taste of beer. Now don’t misunderstand, you can make good beer with most municipal water supplies, but very hard or soft water can make it difficult to brew certain styles of beer.

“Soft” water contains low concentrations of dissolved salts, particularly salts of calcium. “Hard” water contains high concentrations of salts, mainly calcium bicarbonate or calcium sulfate. “Temporary hardness” is a term used to describe water content. It is caused primarily by calcium bicarbonate and gets its “temporary” name because if the water is boiled, bicarbonate is converted to carbonate which precipitates leaving the clarified water “softened”. In comparison, “permanent hardness” is mainly caused by calcium sulfate, and this remains in solution even after boiling. The distinction is important if the water is to be used for mashing and even more so for sparging.⁽¹⁾

Minerals and their associated ions can have an impact on flavor, aroma, color, head retention, alcohol, and stability of beer. In other words, just about every aspect of beer. The mineral content is largely influenced by its source, whether it is surface water (lakes and rivers) or from underground sources. Even cities from the same region can have dramatically different water profiles as seen in the table below (Table 1).

 

The primary ions important to brewers are calcium, sulfate, sodium, magnesium, and chloride, but there are some secondary ions that can influence brewing chemistry in large numbers. These secondary ions include Iron (Fe +1, +2), Copper (Cu +1), Zinc (Zn +2), and Manganese (Mn +2). Calcium ions (Ca2+) serve several important functions in brewing. They react with phosphates that are present in malt to acidify the mash. Acidification is an important step in creating an ideal environment for protein and starch reducing enzymes to work (See post on Mashing). The increased acidity can lighten the color of wort, increase hop utilization, and favors a reduction in astringent flavors. Calcium ions favor the formation of a good hot break (trub) and yeast flocculation, but they seem to have little effect on flavor^(1,2).

Sulfate ions (SO₄) are the major counter ions to calcium and magnesium ions in permanently hard water. They contribute to a drier, bitter flavor in beers that should be balanced by appropriate amounts of chloride ions. Yeast metabolize sulfates producing small amounts of hydrogen sulfide (H₂S), sulfur dioxide (SO₂), and other substances that contribute to the aromas of beers brewed with sulfate-rich water. The classic example is the `Burton nose' of the ales brewed at Burton-upon-Trent^(1,2).

Sodium ions (Na+) occur in some waters and the ion itself has no benefit in beermaking on its own. Sodium ions can impart sour/salty flavors at high concentrations (over about 150 mg/liter). Magnesium ions (Mg +2) are needed by many yeast enzymes, such as pyruvate decarboxylase (important enzyme in ethanol production). The effects of this ion often resemble those of the calcium ion, but the effects on pH from interactions with phosphates are less pronounced. The effects are often about half because this salt is more water soluble. Excess amounts can impart a sour or bitter flavor to beer^(1,2).

In Part 2 we’ll cover how you can adjust your water chemistry.

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1. Stevens, Roger, et al.; "Brewing: Science and Practice", Woodhead Publishing, 2004, ISBN 0-8493-2547-1
2. Papazian, Charlie (2003). The complete joy of homebrewing (3rd ed. ed.). New York: Collins. ISBN 0-06-053105-3.