boiling
The boil
Boil the wort to isomerise hop acids, sterilise it, coagulate protein, drive off unwanted volatiles and concentrate the extract to the target gravity.
What is actually happening
Isomerisation of alpha acids into their bitter, soluble iso form only proceeds at boiling temperature, and slowly. This is why bittering additions go in at the start and late additions contribute almost no bitterness.
Proteins and polyphenols complex and drop out as the hot break, which is what allows the finished beer to be clear and stable.
DMS is generated from a malt precursor throughout the boil and leaves as vapour — but only from an open, vigorous boil. A covered or gentle boil generates it without removing it, which is why it is the classic pale-lager fault.
Typical conditions
| Temperature | 98–102°C |
|---|---|
| Duration | 60–90 min |
| Scale | Used at both homebrew and commercial scale |
Ranges, not targets. These describe what is usual across the styles and breweries that use this step, and a value outside the range is a decision rather than an error.
What goes wrong here
Risks rather than certainties. This step does not cause these faults; getting it wrong can.
- DMS — A cooked-vegetable note from a malt precursor that a vigorous open boil should have driven off.
- Chill haze — A temperature-dependent haze from protein and polyphenol binding — cosmetic only, and by definition it clears as the beer warms.
- Cheesy — A cheesy, sweaty aroma from badly stored hops whose beta acids have oxidised.
Questions
Can I shorten the boil?
Some brewers do, and short-boil beers are made commercially. What is lost depends on the beer: hop utilisation falls, hot break is less complete, and DMS removal is reduced — which matters a great deal for a pilsner-malt-heavy pale lager and much less for a dark ale using little pilsner malt.
Related steps and concepts
- Whirlpooling — What follows it.
- Isomerisation — The reaction that creates bitterness.
- Hot break — The protein coagulation it drives.
Also at the boiling stage
Concentrated lupulin products · First wort hopping · Late hopping · Wet hopping
See the whole process in order on how beer is made.
Last reviewed 2026-08-16.