Brewing a robust porter at home on a small stove

What a robust porter is

Porter began in 18th century London. The robust porter of today is a dark brown to black ale of roughly 5% to 6.5% ABV, with flavours of dark chocolate, coffee, caramel and some burnt grain, balanced by moderate hop bitterness. It is less roasty and dry than an Irish stout. Many brewers describe it as a stout with the edges smoothed off. Our porter guide covers the style's history and variants.

Why a dark beer suits a small stove

A domestic stove struggles to bring 25 litres of wort to a rolling boil. A weak boil is a problem in pale beers, where it leaves cooked sweetcorn flavours and poor clarity. In a porter, roasted malt flavours are big enough that small imperfections are much less noticeable. Pale lagers are a test. A porter is a reward.

The fix for the boil itself is simple: brew smaller. A 10 litre batch in a 15 to 20 litre pot boils properly on most single burners. Partly cover the pot while heating to save time, then take the lid off once it boils so unwanted compounds can escape. On a gas stove use the largest burner. On induction check that the pot base is magnetic.

Measure your own boil-off once with plain water. Boil 12 litres hard for an hour and see what is left. Most home setups lose somewhere between 1.5 and 3 litres an hour. That number tells you how much wort to collect from the mash so you finish at 10 litres rather than 8 or 12.

A 10 litre recipe

For 10 litres at an original gravity of about 1.058, using brew in a bag at about 70% efficiency:

• Pale ale or Maris Otter malt: 2.2 kg (78%)
• Crystal malt, around 120 to 150 EBC: 0.25 kg (9%)
• Chocolate malt: 0.2 kg (7%)
• Black malt or roasted barley: 0.07 kg (3%)
• Munich malt: 0.08 kg (3%)
• Hops: about 30 to 35 IBU from an English or neutral hop such as East Kent Goldings, Fuggle or Magnum, mostly at 60 minutes
• Yeast: an English ale yeast for some fruit, or a clean American yeast for a drier result

Mash at 67 to 68 °C for 60 minutes to keep body and a little sweetness. Our roasted malts guide explains how chocolate, black malt and roasted barley differ. Keep the darkest malts small. A little goes a long way. Too much tastes acrid.

Water and roast

Dark malts are acidic and pull the mash pH down. Hard, alkaline water, common from Indian borewells, actually suits dark beers better than it suits pale ones. If you brew with very soft RO water, the mash may end up too acidic and the roast can taste sharp. A little baking soda or chalk added to the mash helps, but measure carefully. If you are not sure, a blend of RO and tap water is a safe middle ground.

Another trick is to add the darkest malts only for the last 15 minutes of the mash. You still get colour and flavour, with less harshness.

Fermentation and conditioning

Ferment at 18 to 20 °C beer temperature. In warm months that means a water bath with frozen bottles. A porter tolerates a bit of fruitiness better than a pale beer, but above about 23 °C it gets hot and solvent like. Leave it two weeks, check the gravity on two separate days and bottle with priming sugar for about 2.0 to 2.3 volumes of CO2. That is a softer carbonation that suits the style. Porter improves with a few weeks in the bottle. Unlike a hoppy beer it keeps well for months stored cool.

Serving and next steps

Serve at about 10 to 13 °C, warmer than a lager, so the chocolate and coffee come through. It pairs well with grilled meat, mutton dishes and dark chocolate desserts. If you enjoy the result, our guide to brewing a stout at home is the natural next step. Moving between the two teaches you how small changes in roast malt shift a beer's whole character.