Oxalates. Oxalic acid is a dicarboxylic acid found in many locations in nature. Of particular significance for brewing, it is found in malt. It has a high affinity for calcium, which has implications for the body, as the resultant precipitates can lead to problems such as kidney stones in individuals who are otherwise at risk for the condition. In the context of beer, precipitated oxalate in the beer leads to particulate and haze formation, gushing, and the white mineral deposit called “beer stone,” the latter being responsible for the blocking of beer piping. For this reason, oxalate removal is encouraged in the brewhouse by the addition of sufficient calcium to precipitate out the material in mashing and/or wort boiling. The rule of thumb is that there needs to be 4.5 times more calcium present than oxalic acid, but the factors impacting the level of oxalic acid in malt are not well understood.