Brewing Water Tweaks
TroubleShooting
Robb Van Putte — Staunton, Illinois asks,
I am about to brew my first all-grain batch of beer with reverse osmosis (RO) water. I used the EZ Water Calculator spreadsheet to determine mineral additions to the water. Since I am using RO water, I entered in zeros for all of the starting mineral contents. After entering in the grain bill and total water required for the brew day, it determines the amount of salts to add to the water. This, of course, is based on how the grains affect the pH of the mash as well as salts added, with the goal of predicting a mash pH in the range of 5.4–5.6. However, the calculator does not recommend adding any calcium carbonate or sodium bicarbonate to the mash or sparge water. So, here’s my question: Isn’t it recommended to add some alkalinity to the water in order to buffer against pH changes that fall below the optimum? Or is it really dependent on the grain bill, the grist ratio, and the salts added to the strike and sparge water? Here’s the grain bill:
6 lbs. (2.7 kg) pale ale malt
2.25 lbs. (1 kg) Munich malt (10 °L)
0.5 lb. (227 g) caramel malt (60 °L)
0.25 lb. (113 g) Carapils® malt
0.25 lb. (113 g) chocolate malt
0.38 lb. (172 g) white wheat malt
Grain bill, grist ratio (mash thickness), and salt additions all affect mash pH. I am not going to address specific how-to details related to the EZ Water Calculator in this answer, but after playing around with this spreadsheet I can verify that the tool does not “suggest” salt additions to balance the pH; you need to enter values and use an iterative process to dial in the salts to hit your target before you brew. It’s important to understand all calculations in a spreadsheet that someone else wrote and EZ Water looks pretty solid, but I would like to know more about how mash pH is being modeled, but that’s a discussion for another day.
The topic of residual alkalinity (RA) is really at the heart of your question and I will attempt to address RA without the use of much math. The term RA is used by brewers to predict whether brewing water will increase or decrease mash pH above a baseline mash using distilled or RO water. Malt labs around the world use standard lab methods to analyze malt and most of the tests run on malt begin by mashing a malt sample in distilled water. pH is one of the values reported on a standard malt analysis and is usually between about 5.7 to 6.0 for base malts (note that so-called congress mashes are very dilute, 8:1 water-to-grist ratio [3.85 qts. per pound], compared to brewing mashes). Brewing waters with negative RA values will lower the mash pH below lab values and waters with positive RA values increase mash pH above lab values.
Carbonates contribute alkalinity to water while calcium and magnesium ions in water react with malt phosphates to release hydrogen ions. Water has a positive RA when the alkalizing effects of carbonates are greater than the mash acidifying effects of calcium and magnesium. I am not going to get into the weeds of RA calculations because all concentrations are expressed as calcium carbonate equivalents (or calcium oxide equivalents if working with German hardness (˚dh) units) and that is a funky, confusing, and deep topic unto itself, but here is the formula for RA:
Residual Alkalinity (as ppm CaCO3 ) = [Total Alkalinity] – {([Ca+2] ÷ 3.5) + ([Mg+2] ÷ 7)}
Note: [x] denotes concentration expressed as CaCO3 equivalents
The divisors (3.5 and 7) associated with the calcium and magnesium concentrations relate to the solubility and acidifying power of calcium phosphate and magnesium phosphate. The bottom line is that RA is used to describe brewing water and how it relates to mash pH.
Most beer in the world loosely falls into the Pilsner style with malt bills almost entirely made up of pale base malt. In the world of specialty beer, recipes, like yours, are much more diverse and often include higher kilned base malts, like pale ale malt, crystal malts, and roasted grains, all of which are more acidic than pale base malts. What this means to the practical brewer is that Pilsner-type brews almost always require some sort of acid addition, such as acidulated malt, lactic acid, phosphoric acid, or calcium additions to move mash pH into the desired range. Pale ales, amber ales, and brews with just a touch of roasted malts often require little to no acid additions because the special malts used for these brews have sufficient acid to bring the pH into the right zone. And when it comes to darker brews, such as dunkel, porter, and stout, carbonate additions may be required if water does not have enough residual alkalinity to offset the acidic, roasted malts used for these styles. And this is what you have asked about in your question.
Here are a few pointers about the latest version, EZ Water 3.02, that may help you out. This calculator does have a place to adjust the pH up by adding slaked lime, baking soda (my preferred salt for this purpose), or chalk. For your recipe, I started with RO water, entered your grain bill (I used the pH data for Vienna malt for pale ale malt considering similar toast levels), assumed 12 L of water for mashing and 12 L for sparging, then added 3 grams of calcium sulfate and 3 grams of calcium chloride. This combination gave me a mash pH of 5.41, which is right in the sweet spot for mash pH.
To switch things up a bit, I increased the roasted malt to a pound (0.45 kg), bumped the crystal malt up to a pound (0.45 kg) and took out the wheat malt. When these changes are made, the predicted mash pH drops to pH 5.3. This is an example where adding alkalinity is needed to buffer the mash pH up. Step 4b in EZ Water is where you can add in alkalinity, and 2 grams of baking soda added in cell E44 gets the pH back up to 5.41. I hope this answer helps to clarify the oftentimes murky topic of brewing water!
