The mashing at the Zatec brewery,

is a double decoction system – using two 120 hectolitre mash kettles. The mash is heated in the first kettle. Third of the mash is then pumped into the second kettle where the temperature is raised further. The process is repeated with the mash being transferred between the kettles until sacharification. The aim is to release as much brewing sugar as possible from the starch.

The mash is pumped into the lauter tun where it rests for 20 minutes. The lauter tun has a double bottom, one of which is a strainer. The sweet extract or wort is filtered through the strainer and pumped to the brew kettles, where it is boiled with hops for two hours. The extract is closely monitored to ensure that it falls within the necessary levels.

Only Zatec hops used – and are added in three stages. Hops are added after 30 minutes, then after 1 hour and again after 1.5 hours. 270 grams of hops are used per hectolitre of wort. Different varieties of Zatec hops are used - the first two stages use bittering hops, with the final stage using aroma hops.

The hopped wort goes in to the whirpool to extract any large pieces of sediment before passing through a paraflow that cools the liquid to 6 degrees Celsius. Once cooled, the wort passes into open square fermenters built of concrete and lined with epoxy resin. Primary fermentation lasts between 10 and 12 days at a temperature of 8-9 degrees - depending on the strength of the finished beer.

After fermentation in traditional open vessels, each beer is pumped deeper down into the hillside to the rows and rows of conditioning tanks that fill the chilly cellars (constructed in 1863).

The 120 tanks are ranged horizontally. Lagering takes more time when tanks are horizontal meaning that some malt sugars remain in the beer which creates a fuller and more complex product. Lagering takes place at 1 to 2 degrees C.

The 10 degrees beer (4.1% abv) is lagered for 21 - 25 days, the 11 degrees (4.6%abv) for 35 - 40 days, and the 12 degrees (5.3% abv) for 45 - 55 days.

The finished beers are either filtered before bottling or kegging.