Boiling the wort, and boiling equipment
The boil sterilises the wort, concentrates it and is where the hops give their bitterness and aroma.
What the boil does
A rolling boil for 60 minutes does several jobs at once: it sterilises the wort, drives off unwanted compounds such as dimethyl sulfide (which tastes like cooked corn), coagulates proteins so the beer clears later, and isomerises the alpha acids in hops so they taste bitter.
Hop timing
Hops added at the start of the boil give bitterness. Hops added in the last 15 minutes give flavour. Hops added at flameout give aroma. The recipe calculator shows the bitterness each addition adds, using the Tinseth formula.
Keep it rolling
A vigorous boil has large, steady bubbles across the surface. A simmer is not enough. Watch for boil-overs when the wort first reaches the boil, and turn the heat down briefly as the foam rises.
Boiling equipment
You need a large pot or kettle, ideally with 30% more volume than the amount of wort you plan to boil. Stainless steel is the easiest to clean. Aluminium is cheap and works well. Thin enamel pots are fine for small batches but chip easily.
- A kettle larger than your batch, to avoid boil-overs.
- A heat source strong enough for a rolling boil: a gas ring, an induction hob or an electric element.
- A thermometer and a long spoon.
- A wort chiller, or a sink of cold water and ice, to cool quickly after the boil.