right.
The Right Acidity
The enzymes at work in the mash prefer a specific pH, so most brewers aim at between 5.2 and 5.5. That’s pretty much the Golden Rule unless you’re making a sour beer, and even then the drop in pH usually happens during fermentation even when you’re using acidulated malt.
Getting the pH of the mash right is a bit of a battle because the kind of malt you add changes it. Thankfully, most water supplies are slightly alkali and, if you’re lucky, nature can do the work for you because dark malts lower the pH. You can also tweak the mash using brewing salts, but this can have an effect on the flavour of the beer. German brewers—who have to stick to certain rules to adhere to that all-important marketing tool, the Reinheitsgebot—use a little acidulated malt to get the right pH.
The Right Time
You can mash for as long as you want. Usually it’s for around an hour, but for an imperial stout it could be several to convert all the starch. The longer you do it, the more sugar you will extract because the enzymes will have more time to work. A longer mash also allows brewers time to change the temperature of the mash – going through the beta temperatures up to the alpha to break down as much as possible. However, not all mash tuns are set up for this, so most brewers stick to one temperature.
The Right Gravity
Brewing is all about having a clear destination in mind, and in the mash that destination is the correct “original gravity.” This is a measurement of the sugar-to-water ratio in the sugary liquid that is now known as “wort”. Too high and the beer could be more alcoholic than intended, too low and it could be weaker. At the end of fermentation, the “final gravity” – or remaining sugar concentration – is measured and the difference between the two reveals the ABV (alcohol by volume) of the beer.
In homebrewing, the gravity is measured using a hydrometer, which is a long, absurdly thin glass tube that floats in the wort. The original gravity is indicated by how high it sits in the liquid. Ask any homebrewer how many times they have smashed their hydrometer and you will learn what most of them think of this particular piece of equipment. Only a little more robust is the refractometer, which is less accurate but has the advantage of making the brewer look like a pirate.
Getting the right gravity is a tricky little game played by brewers once the mash is over. The malt has been steeped, stirred and broken down to release its sugar, so now the brewer needs to collect it. This is done by opening up the bottom of the mash tun and pouring hot water (around 168ºF) in from the top. This water filters through the grain, collecting all the sugar before making its way into the next vessel, the kettle. This process is known as “sparging” or, when using a second vessel called a lauter tun, “lautering.”
As it goes through, the brewer takes a sample to measure. From that, he works out how much water he’ll need to get the right original gravity. This happens several times during the so-called “run off” because the first few litres of wort are usually more concentrated than the last few. Lovely as water is, the last thing he wants to do is add too much and end up diluting the beer.
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