With water comprising up to 95 percent of the volume, water could well be the single most important ingredient in your home brewed beer. Don't take it for granted! If you need brewing water modifiers to adjust the salt and mineral content in your beer, or to change the softness or focus of the malt and hops in the beer, visit MoreBeer! for water modifiers that can help boost the efficiency of your system. Gypsum is calcium sulfate that is used to add calcium ions to brewing water to permanently harden it. Epsom salt, used at half the levels of gypsum, adds sulfate and magnesium ions to brewing water. Calcium carbonate can be used for temporary hardness in dark beers by adjusting the pH level upward. Burton salts blend gypsum, potassium chloride and Epsom salt for a mixture known as "brewing salts."