The Importance of Geology in the Development of Beer Styles

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Many beer lovers are unaware that beer types were originally highly dependent on the geology of the area where the water used to brew them was drawn.

Think of the regions known worldwide for their beers. The bitter finish of an English IPA, the clean taste of a Czech Pilsner or the dark, almost burnt graininess of an Irish Stout are all attributes of the power of geology.

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Beer is more than 90% water, and the geology through which that water seeps makes all the difference in the final product.

The minerals dissolved in the water can make a beer an outstanding product or simply undrinkable.

Water Cations for Brewing Beer

Among the cations in water, the ions with a positive electrical charge, four are particularly significant for brewing, namely calcium, magnesium, sodium and potassium.

Calcium, for example, is critical for yeast to work efficiently. It also controls the pH of the wort and helps with coagulation and flocculation. That is why distilled water cannot be used as it is to brew beer, and anyone who uses it has to add mineral salts.

In general, soft water favored pale lagers such as Pilsner, carbonate-rich water favored dark beers and sulfate-rich water favored hoppy pale ales.

Water Types and Beer Styles

The fact that certain types of beer develop better with certain types of water was discovered by trial and error long before brewers understood water chemistry.

In Burton-on-Trent, England, the Benedictine abbey was founded around the year 1004, and the first references to its brewhouse date from 1295. Its wells drew water from the Permo-Triassic sandstones rich in evaporites that lie beneath the area.

When sugars are extracted from malted barley in hot water, the step known as mashing, what matters is not the pH of the water but the pH of the mash, which works best between 5.2 and 5.6. Burton’s abundant calcium helps bring it down into that range.

That hard water, rich in calcium and sulfate (295 ppm of calcium, 300 ppm of carbonates and 725 ppm of sulfate, according to the Brewing Waters of the World table), enhances the bitterness typical of classic English beers.

Sulfate enhances hop bitterness, and hops, a natural preservative, helped beer survive sea shipping, as happened, for example, with the birth of IPA beers or “India Pale Ale”.

The soft water of the Pilsen region, in western Czech Republic (7 ppm of calcium, 14 ppm of carbonates and very little sulfate), led to the development of the light, clean-tasting beer that we now know as Pilsner.

The metamorphic rocks underlying Pilsen allow groundwater to move through fractures while dissolving few minerals along the way.

Regions dominated by sandstone and Paleozoic or Precambrian metamorphic rocks have water with low levels of dissolved minerals and ions. This often gives the resulting beer a less distinctive flavor.

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Two Kinds of Guinness Beer

The Porter style developed in 18th century London with carbonate-rich water.

In areas dominated by carbonate rocks, with springs high in calcium and magnesium, controlling the pH of the water and the wort was a major problem.

Later, the Porter style reached Ireland. Arthur Guinness leased the St. James’s Gate brewery in Dublin in 1759 and, years later, began brewing porter, including a stronger or “stouter” version, with water of about 118 ppm of calcium, 319 ppm of carbonates and 54 ppm of sulfate.

Because it flows through limestone, Dublin water is very alkaline. Highly roasted malts acidify the mash and offset that alkalinity, which is why carbonate water pairs well with dark beers.

Black malt was not born in Dublin. Daniel Wheeler patented it in London in 1817, and breweries in both cities adopted it.

There may be some merit, then, in the legend that Guinness brewed a beer in Dublin that tasted different from the one brewed in London.

Although the water of both cities is high in carbonates, the limestone source rocks of the Irish water are Carboniferous, while those of London date from the Cretaceous.

Different levels of magnesium, chloride, sodium and potassium could explain the sweeter taste attributed to the London version.

Availability of Ingredients

With malted barley, hops and yeast available from all over the world, water is often the only local ingredient in beer.

Even so, soil and climate still decide where those ingredients are grown.

In 2024, Washington produced about 74% of the hops grown in the United States, and together with Idaho and Oregon it accounted for virtually the entire national harvest, according to the U.S. Department of Agriculture (USDA).

Frequently Asked Questions (FAQ)

1. Why is geology important in brewing beer?

Geology determines which minerals water dissolves as it passes through rock, and that composition affects mash pH, perceived bitterness and the style that works best with each water.

2. Which beer styles are associated with each type of water?

The very sulfate-rich water of Burton-on-Trent is associated with English pale ales and IPAs, the soft water of Pilsen with Pilsner and the carbonate-rich water of London and Dublin with Porter and Stout.

3. Can the water profile be adjusted to imitate classic styles?

Yes. Many brewers adjust the mineral profile of their water with salts such as calcium sulfate or calcium chloride to approach the conditions of traditional regions like Burton-on-Trent or Pilsen.

4. What pH is targeted when brewing beer?

What matters is the pH of the mash, not that of the water. The usual range is 5.2 to 5.6, and calcium and roasted malts help bring it down, while carbonates raise it.