Porter is a dark ale you can build in a home kitchen from a pale base malt, three small additions of roasted malt and a clean ale yeast. The version worth brewing is defined by which grains those additions are. A modern porter takes its colour and its cocoa depth from brown malt, chocolate malt and a modest amount of black malt, all of them malted barley rather than raw roasted grain. It finishes with enough residual sweetness to hold that roast up instead of letting it dry out on you. What follows is the part a brewer actually needs, which is the grist in weights and percentages, the gravity and bitterness targets for the style as it is brewed today, and the mash temperature that decides how much sweetness survives fermentation. The last section covers the three mistakes behind every ashy or thin home batch.
What A Home Porter Needs
- Keep the roasted grains coarsely crushed or steeped separately, because their harshness reaches the kettle before fermentation even starts.
- Mash hot enough to leave the beer some unfermentable sugar, since a batch that dries out too far drinks thin and tastes of coffee grounds.
- Ferment a clean English or London ale strain between 18 and 20°C, because a warm room turns the beer banana and solvent.
- Weigh the grain rather than measuring it by volume, and keep the percentages rather than the weights in your head when you scale the batch down.
What Makes A Porter A Porter
Porter was London's dark beer of the eighteenth century, and the early versions were built on brown malt rather than on pale. Brown malt is barley kilned hard enough to taste of toast and faintly of coffee instead of biscuit or honey. Black malt arrived in 1817, when the high-temperature roasting process was patented, and it let a brewer get the same near-black colour from a few percent of very dark grain instead of a third of the bill. Chocolate malt sits between those two and contributes cocoa and a soft roast without sharpness. So the modern home grist is pale base malt, brown malt, chocolate malt, a little black malt and some crystal for body. That combination matters because it gives a rounder, sweeter roast than any other dark beer gets.
That is the difference from a stout, and it only needs saying once. A dry stout takes its sharp coffee bite from unmalted roasted barley, while a porter takes its cocoa from roasted malt, which is softer and brings sweetness with it. A brewer can blur that line by putting roasted barley into a porter, and plenty do, but the bill below is what the style is built on.
The Numbers To Aim At
| English porter | American porter | |
|---|---|---|
| Original gravity | 1.040 to 1.052 | 1.050 to 1.070 |
| Final gravity | 1.008 to 1.014 | 1.012 to 1.018 |
| Alcohol by volume | 4.0 to 5.4 percent | 4.8 to 6.5 percent |
| Bitterness | 18 to 35 IBU | 25 to 50 IBU |
| Colour | 20 to 30 SRM | 22 to 40 SRM |
Those are the ranges published in the BJCP style guidelines, which is the reference most homebrewers judge a recipe against. Start in the English column, because it is the smaller beer, it is harder to get badly wrong, and it shows the grain up. A brewer aiming at the American end of the range mostly gets there by adding more base malt rather than more dark grain, which lifts the alcohol and leaves the roast where it was. That is the honest way to read the distance between the two columns, as strength and colour rather than as a heavier hand with the black malt.
A Grist For Nineteen Litres
This is a single-infusion all-grain bill for about nineteen litres of finished beer at roughly 1.050 before fermentation. It assumes an ordinary home system extracting around seventy percent of the available sugar, so measure your own extraction on the first batch rather than trusting the figure. Weigh the grain rather than measuring it by volume, and buy it from a supplier that turns its stock over.
| Grain | Weight | Share | What it contributes |
|---|---|---|---|
| Pale malt, English two-row | 3.4 kg | 75 percent | The backbone, and the enzymes that convert everything else |
| Brown malt | 450 g | 10 percent | Toast and a faint coffee edge, the flavour that says porter rather than stout |
| Chocolate malt | 320 g | 7 percent | Cocoa and soft roast, colour without harshness |
| Black malt | 140 g | 3 percent | The near-black rim in the glass and a dry finish |
| Crystal malt, 60 to 90 Lovibond | 200 g | 4.5 percent | Unfermentable sugar for body and a caramel note |
The percentages are the part worth remembering rather than the weights, because the same bill scaled down to a ten litre batch is the same beer. If the shop has no brown malt, the practical substitute is a little more chocolate malt on a pale base, and the result will read closer to a brown ale with roast in it than to a porter. That is the argument for ordering the brown malt rather than improvising. Keep the black malt low until you know how your own system treats it, because it is the grain most often responsible for a harsh beer, and it is easy to add and impossible to take back out.
Mash Temperature Is Where The Sweetness Comes From
A porter needs residual sugar, not because the style is sweet but because the roast is drying. A beer with no body behind drying grain tastes like nothing except ash. Mash at 67 to 68°C (152 to 154°F) for sixty minutes, which leaves enough unfermentable carbohydrate that a batch on the bill above should finish somewhere around 1.012 to 1.014. Mash five degrees cooler with the same grain and you will land nearer 1.006, at which point the beer drinks thinner than its original gravity suggests and the chocolate malt comes across as coffee grounds. Everything else about the process, conversion, sparging, water and acidity, is the same as it is for any grain batch. What is porter-specific is that you are deliberately trading attenuation for body, so a recipe calculator complaining that the beer is under-attenuated may simply be telling you the beer is a porter.
Hops, Yeast And Fermentation
Bitterness in a porter is structure rather than flavour. Aim at the middle of the range, about 28 to 32 IBU for the English target above, which in a nineteen litre batch is roughly 25 to 30 grams of an average six percent alpha hop boiled for the full hour. Check that weight against the alpha acid figure printed on your packet and against a brewing calculator, because grams mean nothing without the percentage behind them. Varieties with a herbal or earthy character suit this grain better than intensely citrus ones. One small addition with ten minutes left in the boil is plenty, and there is no reason to dry hop a porter at all.
Yeast is the other half of the style. Choose a clean to lightly fruity ale strain, the kind sold as English or London style, and let it work between 18 and 20°C, where it produces restrained dark-fruit esters that sit with brown malt the way plum sits with toast. Ferment the same strain at 23°C because the summer room is warm, and it will throw banana and a solvent edge that have nothing to do with porter. That is the single most common reason a home version stops tasting like the beer the brewer intended. Use the whole packet of dry yeast rather than half of it to save money, keep the vessel out of direct light, and leave the beer a few extra days at fermentation temperature near the end so the yeast can tidy up after itself.
Carbonate it moderately, less than you would a pale ale, and hold the bottles at room temperature for about two weeks before the first one goes into the fridge. A porter tasted four days after bottling is usually judged harsher than it actually is.
Three Mistakes That Make A Home Porter Ashy Or Thin
- Treating dark grain like any other malt. Roasted malt contributes no enzymes and a great deal of astringency, so a flour-fine grind, a long rinse over a dark bed, or a sparge run until the gravity collapses will pull harsh, drying notes into the kettle before fermentation starts. Crush the dark grains coarsely or leave them whole. Better still, steep the black malt separately in warm water and add that liquid to the boil to taste, which lets you set the roast level by drinking rather than by arithmetic.
- Chasing efficiency at the expense of body. Mashing cool and sparging hard both strip the very thing this style runs on, so take the lower extraction, brew a smaller volume, and let the beer finish where the style finishes. A porter that comes out at 1.006 is not a more efficient batch of porter. It is a different and worse beer.
- Building the roast out of roasted barley because that is what the dark beer kit in the cupboard contains. It is the stout grain, it is sharper and more astringent than roasted malt, and in a porter it reads as acrid within a couple of sips. A small amount will not wreck a batch, but a grist where roasted barley does the work black malt should be doing has changed the beer you set out to make.
Frequently Asked Questions
Can I brew a porter with malt extract?
Yes, and it is a sensible way to make this beer without a mash tun, with one limitation worth knowing. Extract supplies the fermentable sugar and a base malt character somebody else chose, so all of the dark grain has to come from a steep. A steep is also where the astringency mistake gets made most often. Keep the steeping grains around 65 to 70°C, lift them out after about half an hour, and do not rinse them, because that rinse is what drags harshness out of the husks. The targets, the yeast choice and the fermentation temperature above all apply unchanged.
Why did my home porter turn out thin and harsh?
Almost always the same two causes, which are too little residual sugar and too much from the roast grain. Check the finish gravity against the target before touching the recipe, because a porter that ended at 1.006 was mashed too cool. No amount of crystal malt will put body back into a beer the yeast has already dried out. Then look at how the dark grain went into the kettle, since that is where the harshness came from, and change one of the two rather than both at once.
How long should I wait before opening a bottle?
Two weeks at room temperature and then cold, and the honest answer is that a porter built on brown malt keeps improving for another month after that. The roast softens, the residual sweetness comes forward and the beer stops tasting of the process that made it. If you cannot wait, drink it young and pull half the black malt out of the next batch, since a young bottle is when that grain is loudest.
Is porter a good choice for a first batch?
It is a better first batch than most people expect, because dark malt hides a rough process far more effectively than a pale ale does. In a pale ale, every grain decision is exposed and any faded hop aroma is obvious immediately. Porter is not foolproof either, since the usual outcome of a first attempt is not a ruined beer but a harsh one. The way to avoid even that is to read the grist and set the mash temperature before you buy the grain.
Brew It Twice And Change One Thing
Make this bill once exactly as written, measure the gravity going into the fermenter and coming out of it, and write both down beside the date. Then brew it again with one variable moved, two degrees on the mash or half the black malt, and taste the two bottles side by side rather than one after the other an hour apart. Porter is a style where a single percentage of one grain is the distance between cocoa and coffee grounds. The second batch will teach you more about your own kettle and your own palate than any recipe, including this one, is capable of teaching.
