We have a whole-house R/O (reverse osmosis) water treatment system in our current home. The water tastes good but the beer we have made from it seems, perhaps, less complex and less bright than beer we’ve made with non-R/O tap water in previous residences. Is there a standard set of minerals/additives that could be added to make the R/O water appropriate for most beers, or is the only way to select additives to test the water and then craft the minerals to be added based on the beer style we are planning to brew?
Debbie Sellmeyer
Pasadena, Maryland

I have spent the last 20 years brewing beer using pure water, either from RO or distillation, and to me this has become the norm. I like brewing with RO because it takes variability away from water and gives the brewer a blank slate, but as you point out that slate needs to be decorated.
   
The most important mineral in brewing water is calcium. Calcium interacts with polypeptides and phosphates from malt to affect mash pH, it stabilizes alpha-amylase, is involved in break formation in wort and also influences yeast. You can add calcium from two primary sources; calcium sulfate (gypsum) and calcium chloride. Sulfate and chloride both affect beer flavor and sulfate accentuates bitterness and dryness while chloride is known to give beer a rounder and fuller palate. I like using a blend, and I target a calcium level in most of the beers I formulate of somewhere between 25 and 100 mg/L. If you want an assertive mineral character to your beer you may want to use calcium levels up to 200 mg/L.
   
While calcium, and to a lesser extent magnesium, causes mash pH to go down, or become more acidic, the carbonate and bicarbonate ions cause mash pH to increase. Most beers brewed in the world tend to be lighter in color and do not benefit from carbonate in water. Darker beers, however, incorporate dark malts into their recipes and these malts frequently result in mash pH that is too low. The ideal mash pH range is 5.2–5.4 and if the pH is too low carbonate species will help move the pH back into this window. When using RO water it is easiest to use sodium bicarbonate as the source of “carbonate” since calcium carbonate is not soluble in water unless the water is acidified. Sodium bicarbonate, on the other hand, is much easier to use. If you want to brew a stout using RO water you probably want to target about 50 mg/L of bicarbonate using sodium bicarbonate.
   
I named two more flavor active ions in the previous paragraph: magnesium and sodium. Magnesium is one of the key components found in Burton water, although the term “Burtonize” has somehow evolved to mean simply heaping in a pile of gypsum to water. Real Burton water is quite high in magnesium, which is significant because magnesium has a pronounced bitter/metallic flavor and that does indeed affect beer flavor. Magnesium is also a laxative. Most beers in the world do not have much magnesium and I would not intentionally add more than about 50 mg/L of magnesium from magnesium chloride if I were experimenting with this particular salt. Sodium is also flavor active and some people automatically have a negative opinion of sodium because who wants salt in beer . . . or perhaps I should have asked why the German beer Gose has salt added to it in high doses? As it turns out, sodium is not perceived as salty in beer until the content exceeds about 40 mg/L. At lower levels it influences the perception of sweetness and palate fullness. I add about 10 mg/L of sodium with Kosher salt when brewing a variety of beers, especially pale lagers.
   
Minerals are not the only thing to consider adding to RO water. Lactic acid can be added to adjust mash and wort pH if the pH is too high and the affect that lactic acid has on flavor is completely different than achieving the same change in pH using calcium salts. Yes lactic acid is tart, but that is not what it does to beer flavor when used to make small modifications to pH in the brewhouse. Lactic acid adds complexity and makes a crisper, brighter beer when used in styles that can suffer from what winemakers call flabbiness or lacking in the acidity department.
 

I’ve been brewing ales for a while and want to try my hand at a few lager recipes I’ve created. If I were to do my primary fermentation at 50 °F (10 °C), and my secondary at 45 °F (7 °C), would I have to let the beer warm to room temperature to bottle with priming sugar? I know ale yeast goes dormant in the fridge at low temperatures, but lager yeast thrives in those conditions. So I am not sure if the bottles would carbonate at a temperature range between 40–50 °F (4–10 °C)?
Nic Ashley
Raleigh, North Carolina

Since you are new to brewing lagers, I would focus 100% of my attention to primary fermentation and how the yeast behaves when fermented at cooler temperatures. Ale brewers are accustomed to having aggressive behavior during primary fermentation and the aroma coming from the fermenter is usually quite nice. Lagers are a different creature all together. Lager fermentation activity is often perceived by the eye as weak, and aromas like rotten egg and burning match are not uncommon. These two features often take some time to get to know. It’s important to have some experience so that you know what works.
   
So your first priority is to get your hands around the primary fermentation so you recognize “normal” from “odd” and so you know what times and temperatures seem to work for the strain or strains you select. I would not get worked up about bottle conditioning because the strain used in bottle conditioning typically has very little effect on beer flavor; there is simply so little sugar that is metabolized by the yeast during conditioning that the small amount of flavor compounds excreted from the cells during that stage of the game pales in comparison to what is produced during the primary fermentation. Some yeast strains added for conditioning, like Brettanomyces, are a different story and can have dramatic effects on beer during extended aging.
   
If you feel more comfortable adding a small amount of ale yeast and conditioning at room temperature, I would go ahead and do that — knowing that you are in the stages of learning. If you want to go full throttle from day one and naturally carbonate with lager yeast, that will work, too, since historically carbonation was one of the several important changes that occurred during lagering. The thing that you do need to bear in mind is that when lager brewers use the kräusen method they add fresh yeast after primary fermentation is complete, which helps fermentations finish and also helps for a more rapid and effective maturation process. If you do not kräusen you probably should consider adding a small dose of fresh yeast when bottling (about 20 mL of yeast slurry will provide around 1 million cells/mL) and consider conditioning at room temperature to make sure that your beer comes into condition.