Russian imperial stouts are big beers with lots of roast flavor. They are frequently heavily hopped as well. (The BJCP give the OG range as 1.075–1.115, with 50–90 IBU of bitterness.) There’s a lot of variation among commercial examples. The level of roast, the amount and character of the hops, sweetness, the level of carbonation, and the level of yeast-derived esters all vary.
In addition, the character of this beer can change with age. With its high alcohol content and dark malts, it is particularly well-suited to cellaring. In the best examples, aging adds Sherry-like notes to the beer. Of course, some of the hoppier examples are best consumed when they are fresh, before their hop character begins to deteriorate. For beers that are aged, barrel aging and especially bourbon barrel aging are popular options.
It Can Be Difficult Going To The Dark Side
Brewing a Russian imperial stout can be a challenge. You have all the challenges of a big beer, with the added factor of a high percentage of dark grains. Darkly-roasted malts (and dark grains ) lower the pH of the mash and can also lend some astringency to the beer. In the amounts they are used in imperial stouts, the brewer needs to address these issues. In this series of articles on Russian imperial stout we’ll examine water treatment, including the benefits to treating your strike water and sparge water differently. We will look at malt selection, with a focus on flavor, but also how it affects foam color. We’ll look at recipe formulation and wort collection together, because how you plan to collect your wort will affect how you formulate your recipe. [Do you want to fully sparge your grain bed, then boil for hours? Or do you want to collect only the first wort, for shorter boil (at the expense of lowering your extract efficiency)? If you do, can you brew a second beer from the remaining carbohydrates left in the mash?] We’ll discuss the challenge of fermenting such a big beer. And finally, we’ll discuss aging, including barrel aging options and how to mimic (some aspects of) barrel aging in a carboy.
Water Chemistry Review
When pale base malts — such as 2-row pale malt or Pilsner malt — are mashed with distilled water, the pH usually settles into the 5.7–5.8 range. If calcium ions are added to the water — for example, by dissolving the minerals gypsum or calcium chloride in the water — the pH is lowered. A chemical reaction between the calcium ions and phosphates from the malt is responsible for this. Magnesium also lowers mash pH, although to a lesser extent. Specialty malts that are more highly roasted than base malts show a lower pH when mashed with distilled water. If you look at crystal malts, there is a fairly strong correlation between color and acidity – the darker they are, the more acidic they are. However, darkly roasted malts all seem to contain at least roughly the same amount of acidity, on par with some of the darker crystal malts (80–120 °L), not the higher levels of acidity their color would imply.
In pale beers, the presence of calcium ions and some crystal malts help bring the pH down from the distilled water range into a more reasonable mash pH range. In contrast, the presence of bicarbonate ions – perhaps from the addition of sodium bicarbonate (baking soda) — raises the pH of a mash by neutralizing acid. Calcium carbonate (chalk) also raises mash pH, but to a much lesser extent as it also adds calcium to the mash. In beers with lots of dark grains, you may need to add bicarbonate ions to your strike water so that the mash pH does not fall too low.
In practice, most homebrewers rely on a brewing water calculator to calculate their mineral additions, and other adjustments, to the brewing liquor. There are many online. (For whatever it’s worth, most often I use John Palmer’s spreadsheet or the mini water calculator in my own recipe calculation spreadsheet.) These calculators generally work by calculating the residual alkalinity (RA) of the brewing water. This is essentially the amount of alkalinity (the ability to neutralize acid) “left over” after the effect of the calcium and magnesium ions are taken into consideration. Given a beer’s color, the calculator determines how much alkalinity (often expressed as the alkalinity as CaCO3) is required to counteract the acids from the dark grains. This formula works well for pale to light brown beers. However, for the darkest beers, as progressively higher percentages of darkly-roasted grains are used, these calculators progressively overestimate how much bicarbonate is needed to counter acids from the dark grains. In the next installment in this series, which I’ll post on Friday, I’ll explain how to compensate for this, and how to know if you’re adding too much bicarbonate to your water.
In the next article in this series, I will discuss strike water preparation.