Calcium (Ca+2)
Atomic Weight = 40.0
Equivalent Weight = 20.0
Brewing Range = 50-150 ppm.
Calcium is the principal ion that determines water hardness and has a +2 charge. As it is in our own bodies, calcium is instrumental to many yeast, enzyme, and protein reactions, both in the mash and in the boil. It promotes clarity, flavor, and stability in the finished beer. Calcium additions may be necessary to assure sufficient enzyme activity for some mashes in water that is low in calcium. Calcium that is matched by bicarbonates in water is referred to as "temporary hardness". Temporary hardness can be removed by boiling (see Bicarbonate). Calcium that is left behind after the temporary hardness has been removed is called "permanent hardness".
Magnesium (Mg+2)
Atomic Weight = 24.3
Equivalent Weight = 12.1
Brewing Range = 10-30 ppm.
This ion behaves very similarly to Calcium in water, but is less efficacious. It also contributes to water hardness. Magnesium is an important yeast nutrient in small amounts (10 -20 ppm), but amounts greater than 50 ppm tend to give a sour-bitter taste to the beer. Levels higher than 125 ppm have a laxative and diuretic affect.
Bicarbonate (HCO3-1)
Molecular Weight = 61.0
Equivalent Weight = 61.0
Brewing Range = 0-50 ppm for pale, base-malt only beers.
50-150 ppm for amber colored, toasted malt beers, 150-250 ppm for dark, roasted malt beers.
The carbonate family of ions are the big players in determining brewing water chemistry. Carbonate (CO3-2), is an alkaline ion, raising the pH, and neutralizing dark malt acidity. Its cousin, bicarbonate (HCO3-1), has half the buffering capability but actually dominates the chemistry of most brewing water supplies because it is the principal form for carbonates in water with a pH less than 8.4. Carbonate itself typically exists as less than 1% of the total carbonate/bicarbonate/carbonic acid species until the pH exceeds 8.4. There are two methods the homebrewer can use to bring the bicarbonate level down to the nominal 50 - 150 ppm range for most pale ales, or even lower for light lagers such as Pilsener. These methods are boiling, and dilution.
Carbonate can be precipitated (ppt) out as Calcium Carbonate (CaCO3) by aeration and boiling according to the following reaction:
2HCO3-1 + Ca+2 + O2 gas --> CaCO3 (ppt) + H2O + CO2 gas
where oxygen from aeration acts as a catalyst and the heat of boiling prevents the carbon dioxide from dissolving back into the water to create carbonic acid.
Dilution is the easiest method of producing low carbonate water. Use distilled water from the grocery store (often referred to as Purified Water for use in steam irons) in a 1:1 ratio, and you will effectively cut your bicarbonate levels in half, although there will be a minor difference due to buffering reactions. Bottom Line: if you want to make soft water from hard water (e.g. to brew a Pilsener), dilution with distilled water is the best route.
Sulfate (SO4-2)
Molecular Weight = 96.0
Equivalent Weight = 48.0
Brewing Range = 50-150 ppm for normally bitter beers, 150-350 ppm for very bitter beers
The sulfate ion also combines with Ca and Mg to contribute to permanent hardness. It accentuates hop bitterness, making the bitterness seem drier, more crisp. At concentrations over 400 ppm however, the resulting bitterness can become astringent and unpleasant, and at concentrations over 750 ppm, it can cause diarrhea. Sulfate is only weakly alkaline and does not contribute to the overall alkalinity of water.
Sodium (Na+1)
Atomic Weight = 22.9
Equivalent Weight = 22.9
Brewing Range = 0-150 ppm.
Sodium can occur in very high levels, particularly if you use a salt-based (i.e. ion exchange) water softener at home. In general, you should never use softened water for mashing. You probably needed the calcium it replaced and you definitely don't need the high sodium levels. At levels of 70 - 150 ppm it rounds out the beer flavors, accentuating the sweetness of the malt. But above 200 ppm the beer will start to taste salty. The combination of sodium with a high concentration of sulfate ions will generate a very harsh bitterness. Therefore keep at least one or the other as low as possible, preferably the sodium.
Chloride (Cl-1)
Atomic Weight = 35.4
Equivalent Weight = 35.4
Brewing Range = 0-250 ppm.
The chloride ion also accentuates the flavor and fullness of beer. Concentrations above 300 ppm (from heavily chlorinated water or residual bleach sanitizer) can lead to mediciney flavors due to chlorophenol compounds.
