A small quantity of hops, (2 oz or 90 grammes) are put into the wort in the boiler and the whole is boiled for another 1.5 hours.

There are several varieties commonly in use in the UK, each of which has it's own aroma and bitterness.

During the boil the alpha acid content of the hops emparts bitterness to the beer. The essential oils that provide an aroma will boil off.

15 minutes before the end of the boil, a further 0.5 oz or 20 grammes of hops are sometimes thrown into the boil to improve the aroma.

"Irish Moss", which is in fact dried seaweed may also be pitched in at this point to assist with coagulation of the Trub i.e. the gunjey bits you don’t want, in the boil.