The Quiet Ingredient
Why Water Shaped Beer Style
Water is the largest ingredient in beer by volume, and for a long time it determined which beer could succeed in a given place. Soft water favored pale, hoppy beers, while carbonate-rich water favored dark ones. Here's how that connection works and why it's different today.
What water do you need to brew beer?
A glass of beer is, by the greatest margin, water. Malt, hops, and yeast supply color, bitterness, alcohol, and aroma, but they float in a liquid that is never entirely neutral itself. Every natural water carries dissolved minerals: calcium, magnesium, bicarbonate (the salt that precipitates out as limescale during boiling), sulfate, chloride, sodium. How much of each depends on which rock the water has seeped through. Granite releases almost nothing, while limestone and gypsum give up a great deal.
Brewers therefore first need clean water that is hygienically sound and tastes of neither chlorine nor iron. After that comes the finer question: does the mineral mix suit the beer I want to brew? A pale pilsner calls for something different than a black stout. For centuries, this second question decided which beers turned out well in which city and which did not.
How did water historically determine beer style?
Before the 19th century, nobody could deliberately alter their water. Brewers used whatever the well, river, or spring provided. Those with soft, mineral-poor water got a delicate, clear beer with fine hop bitterness from pale malt. Those with hard, lime-rich water often failed with pale malt: the beer tasted flat, and the bitterness turned harsh. With dark, roasted malt, though, it worked very well indeed.
Over generations, this gave rise to brewing landscapes shaped by water. Pilsen, with its very soft water, became the home of the pale, hoppy lager. Burton upon Trent in England, with its gypsum-rich well water, delivered dry, pointedly bitter pale ales. Munich, Dublin, and London were known as cities with carbonate-rich water and were famous for dark beers. The brewers didn't understand the chemistry, but they noticed what worked, and they stuck with it.
What exactly does water do in the brewhouse?
The most important effect shows up during mashing, when crushed malt is steeped in warm water and enzymes convert starch into sugar. These enzymes work best in a slightly acidic environment. Bicarbonate in the water buffers that acidity and pushes the pH upward, while calcium and magnesium pull it back down. In 1953, the brewing chemist Paul Kolbach summed up this tug-of-war in a single figure: residual alkalinity. It shows how strongly a given water raises the pH of the mash.
Dark roasted malts bring their own acidity along. That's why they tolerate hard, carbonate-rich water, while pale malts in the same water don't have enough acidity to balance it out. Further along in the process, water keeps working: on the yield of bitter compounds during the boil, on the yeast's performance, and on the flavor in the glass. Sulfate makes bitterness taste drier, chloride rounds out the body. The next section explains these connections in more detail.
Does water still determine style today?
Barely. Nowadays almost every brewery treats its water: softening it, filtering it nearly mineral-free through reverse osmosis, or adding salts in precise amounts. A pilsner can now be brewed in Burton, and a stout in Pilsen. The claim that "water makes the style" describes history, not the present. Today, malt, hops, yeast, and process matter more in defining a beer style.
Still, it's worth knowing the old water landscapes. They explain why a Bohemian pilsner feels so soft, why an English bitter finishes so dry, and why Munich beer was originally dark. Anyone recreating a style today is often, in effect, recreating that historical water. The following sections move from the chemistry to the famous brewing towns, and then to modern water treatment.