Porter is a versatile beer style. It’s related to stout, and can have a strong, darkly roasted malt character. Or, it can have a mildly roasty, often chocolate-y, flavor. The meekest porters border on being a brown ale. The BJCP separates English-style porters into two categories, robust porter and brown porter. However, you can brew great porters anywhere on the continuum between strongly roasted and mildly roasted. (There are also Baltic porters, which I’m not going to discuss in this article.)
Porters are average strength ales. Many classic examples fall in the 12–14 °Plato (OG 1.048–1.056) range and ferment out to make beers around 5% to 5.5% alcohol by volume. (I’ll reproduce the BJCP stats below.) Porters are generally moderate to full bodied, not dry (like a dry stout) or sweet (like a sweet stout). The roast flavor is complemented by the hop bitterness, often centering around 25 IBUs. The best porters balance all these elements into a flavorful, but well-integrated, beer. Although the roast character is prominent, no single element should completely overshadow the others and no single element is going to make or break your porter.
In this series, I’ll discuss brewing porters on home, with a focus on your water (today), dark malts and special techniques for all-grain and extract brewers. I’ll also discuss specialty porters, including smoked porter, coffee porter and vanilla porter.
Dark Grains and Mash pH
Darkly roasted grains are more acidic than pale malts. In a dark beer, they can cause the pH of the mash to drop below the optimal range (pH 5.2–5.6). This will negatively effect the ability of the amylase enzymes to convert the starches from the malt and the resulting beer may taste overly acidic. Low wort pH can lower hop utilization and make the finished beer taste thin. It also masks the flavor and aroma of the dark grains. However, if the brewing liquor (treated brewing water) contains enough carbonates, the excess acidy is neutralized. In a dark beer, if the mash pH falls into the right zone, the post-boil pH and finished beer pH should also fall in line. Carbonates can be added to the mash by adding either calcium carbonate (chalk) or sodium bicarbonate (baking soda).
Adjusting Mash pH
To calculate the amount of chalk or baking soda, you can use any of the numerous brewing water calculators available online. (I like John Palmer’s water spreadsheet.)
In any beer, you need calcium ions in the mash (for a variety of reasons, including stabilizing the amylase enzymes). However, calcium ions — via a reaction with malt phosphates — also lower the pH of the mash. So, when making your brewing liquor for a porter, you want to have sufficient calcium, but not too much more as you’d simply need to add more carbonate to counteract it. At a minimum, you should have at least 50 ppm calcium in your water, with 100 ppm being better. I like to shoot for roughly 100 ppm calcium and around 300 ppm of carbonates (or roughly 300 ppm alkalinity as CaCO3) for my porter water.
If your water is lacking in both calcium and carbonates, add chalk (calcium carbonate) until you reach 100 ppm calcium, then add baking soda to reach your carbonate target. If your calcium levels are at or above 100 ppm, use baking soda to treat your water. Be aware, however, that adding baking soda could result in sodium levels exceeding 100 ppm, which you don’t want. (In 10 gallons (38 L) of water, 13 g of baking soda would yield 94 ppm sodium, assuming the initial level was 0 ppm.) If your tap water has high levels of calcium, try diluting it with distilled water until you reach a reasonable level, then add baking soda as needed.
If you start with 10 gallons (38 L) of distilled or RO water, adding 3 g of gypsum, 3 g of calcium chloride, 6 g of chalk and 9 g of baking soda would yield a brewing liquor suitable for brewing a porter. This also yields a chloride to sulfate ratio around 1:1. In a brown porter, you might want to slightly shift the balance towards chloride. In a robust porter, you might want to shift the balance slightly towards sulfate.
Brewing Liquor for Extract Brewers
Extract brewers do not need to worry about their mash pH or calcium levels in their brew. The malt extract should have sufficient calcium. However, the dark grains — whether steeped or partial mashed — can still lead to an overly acidic brew. If possible, adjust your carbonate levels by adding some baking soda. If you use 5.0 gallons (19 L) of distilled water as your brewing liquor, adding 9 g (about 2 tsp.) of baking soda will add enough acid to neutralize any excess acidity.
Many extract beers do not require any water treatment beyond filtering out or otherwise neutralizing chlorine compounds. However, as it’s one of the darkest brews, adjusting your brewing liquor will help your extract porter be it’s best, especially if you have soft water or water that’s low in carbonates.
In the next installment in this series, I’ll discuss dark malts and formulating a porter recipe.
BJCP Guidelines for English Porters
stats Brown (12 A) Robust (12 B)
OG 1.040–1.052 1.048–1.065
IBUs 18–35 25–50
FG 1.008–1.014 1.012–1.016
SRM 20–30 22–35
ABV 4–5.4% 4.8–6.5%