Basic Water Chemistry
You know H2O? Basic water class dismissed. Unfortunately, water is never just water. Dissolved solids including chalk, calcium, salt, and others alter water's basic chemical properties.
Hardness and Alkalinity
Years of soap commercials have promoted the term “hard water.” Water hardness measures dissolved calcium and magnesium ions. The reason soap companies care is because hard water interferes with soap's cleaning ability, requiring more soap and causing residual soap film and scale.
Alkalinity measures dissolved bicarbonate and carbonate. These powerful buffering agents interact with dissolved calcium and the acidity released from dark malts. Carbonate-rich brew waters make fantastic bases for stouts and porters.
Generally, not all the carbonates are needed to buffer the mash reaction and grains. Residual alkalinity (RA) is the measure of how much alkalinity remains. For pale beers, too high an RA can interfere with the flavor, requiring hardness additions to balance it out. Conversely, areas of water too low in alkalinity will require the addition of minerals like calcium carbonate to bring up the alkalinity for darker beers.
Don't use water passed through an ion-exchange water softener. It works by exchanging sodium or potassium ions for calcium and magnesium. The end result is too much sodium or potassium to make palatable brewing water.
pH: Hydrogen Power
The scale measuring a solution's balance between acid and base is called pH. It is the ratio of hydrogen ions (H+) balanced by hydroxide ions (OH–). Greater amounts of hydrogen ions mean a lower pH.
The scale runs from 0 to 14. Numbers lower than 7 indicate an acidic solution, numbers higher than 7 indicate a basic or alkaline solution. Distilled water measures a neutral pH of 7. Battery acid is pH 0, bleach is around pH 13. Beer is typically served between a pH of 4.3 and 4.5.
If your water is fairly normal and you want to ensure a nominal mash pH, Five Star Chemicals has a product called 5.2, which can help adjust your mash into the optimum range without a lot of thought.
To all-grain brewers, proper pH ensures complete grain conversion. Optimum conditions require a mash pH between 5.2 and 5.8. This is not your unmixed water's pH. Brew waters settle close to this mash pH range mixed with normal grain bills, so water pH only matters in extremes. With extremely pale or dark grain bills, you want to pay attention to the mash pH and where it settles during conversion. To measure your pH, purchase pH paper strips that measure in the range between 4 and 9. Follow the instructions to read the results.
Flavor Impact of Water
Not surprisingly, the minerals dissolved in your water have a profound impact on your beer. These ions do everything from adjust the chemistry of the mash to boosting hop and malt flavors. Where older brewers restricted their styles to those that tasted right with their water, you can adjust your ion levels to meet your needs.
The Major Water Elements
Bicarbonate (HCO3-1) — The dominant form of carbonate. A powerful acid buffer, carbonates neutralize the acidity of dark-roasted malts and reduce hardness by binding with calcium when boiled. If your water is too high in carbonates (200+ ppm), see below to treat it for paler beers.
Calcium (Ca + 2) — Lowers the mash pH naturally by binding with malt phosphates and is the primary component of water hardness. It has no flavor impact and extract brewers don't need to add it. For all-grain, calcium is a vital catalyst for mash reactions.
Chloride (Cl - 1) — One half of table salt. Has no chemical impact, but leaves your beer tasting fuller and accentuates malt character. Don't overdo it.
Magnesium (Mg + 2) — Reduces mash pH, but less than calcium. Yeast need a small portion (around 20 ppm). Too much adds sour and harsh tastes. Malt generally provides enough.
Potassium (K + 1) — Blocks enzymatic reactions in the mash. Usual metropolitan levels fine for brewing.
Sodium (Na + 1) — Boosts apparent flavors. In heavier concentrations, makes beer taste salty. When combined with hop boosters like sulfate, bitterness is very harsh.
Sulfate (SO4) — Normally bound to calcium, sulfates boost the perception of hop bitterness in levels under 400 ppm. The beer tastes crisper and zippier.
Taste Testing
After tasting grain and hops, it's time to taste the water. For each salt, add a gallon's dose to a quart of distilled water. Bring to a boil with one-third cup of DME and a few hop pellets. Strain and cool the wort. Set aside in sanitized jars and make a whole panel. Pour each sample into clean plastic cups and take notes on the differences. If you don't have any DME, just boil the water without hops.
Calcium carbonate, is tough to dissolve. Add a milliliter of lactic acid to your water if you're using no DME before boiling.
