Brewing with a kveik: hot, fast, with no temperature control

What makes them special

• Temperature: 25 to 40 °C depending on the strain, with an optimum often at 30-35 °C. Below 20 °C they fall asleep. A room at 28 °C in August, a fermenter in a cool box with a hot-water bottle, or simply wort pitched at 35 °C that cools slowly: anything will do.
• Speed: primary fermentation in 48 to 72 hours; a beer can be bottled on the sixth day and drunk in the third week.
• Cleanness: when hot, few fusel alcohols and heavy esters; the profile is fruity (orange, mandarin, tropical fruit) and clean. Some strains are almost neutral and imitate a lager at 30 °C.
• Flocculation: most flocculate very strongly and give a brilliant beer within a few days; a few (Hornindal) stay in suspension for a long time.
• Alcohol tolerance: 12 to 16 % for several strains.
• Low dose: traditionally, Norwegian brewers pitch very little yeast (a tenth of a classic dose), which accentuates the fruitiness. With a normal dose, the profile is cleaner.
• Hunger for nutrients: they need more nitrogen than classic yeasts; without nutrient, they slow down towards the end and can leave sulphur.

The common strains

The strains are sold dry or liquid by the usual yeast labs, sometimes under a trade name; the ingredient equivalences link the trade name to the original strain.

How to brew with them

1. Recipe: kveik like rich worts; a pale ale or an IPA of 1.050 to 1.065 is a good start. Fruity hops (Citra, Mosaic) pair with the orange of Voss. A pils with Lutra is the neutrality test.
2. Nutrients: half a teaspoon of yeast nutrient for 20 litres, in the last 10 minutes of the boil. This is not optional.
3. Chill the wort to 30-35 °C only, which is quick and saves water; pitch.
4. Dose: one 11 g sachet of dry yeast for 20 litres, or half for a fruitier profile; for liquid, one pack without a starter. The yeast pitching rate tool gives the classic dose, which you can divide by 2 to 4 for a kveik.
5. Ferment at 30-38 °C depending on the strain. Hold the temperature: a kveik that cools below 20 °C during fermentation stops and leaves a high gravity. In winter, a cool box with a hot-water bottle or a heating belt; in summer, nothing.
6. Measure the gravity on the third day: the final gravity is often reached. Leave two more days in the warm for the yeast to finish and clean up.
7. Dry hop if planned; in the warm it is very fast (2 days are enough, see dry hopping).
8. Bottle as usual; refermentation at 20 °C works, and at 30 °C it takes a week.

Reusing and keeping the yeast

It is the tradition, and it works: harvest the krausen (the foam of the second day, the richest in healthy yeast) or the sediment at the end of fermentation, keep it in a sanitised jar in the fridge for several months, and repitch with a tablespoon for 20 litres. Kveik also withstand drying: spread a thin layer of sediment on baking paper, dry at room temperature for two or three days away from dust, store dry and cool; they wake up months later. It takes impeccable hygiene, and a culture must be abandoned as soon as a beer has an unexplained fault.

The limits

• The profile is not that of an English or Belgian yeast: no kveik for a typical bitter or a classic tripel, even if the result can be good.
• Underpitched and underfed, a kveik leaves sulphur and a high gravity.
• A fermentation at 38 °C gives off a lot of CO2 and can overflow: leave 25 % headspace.
• Very hoppy beers fermented at 35 °C lose more hop aroma during fermentation; the dry hop is done afterwards.
• Speed does not excuse you from waiting for a stable gravity before bottling.