This again occurs in both the mash tun and the copper. If oxalates are not removed they can cause hazes in finished beers and also contribute to the formation of beerstone in FV's, CT's and casks. Oxalates are also thought to promote gushing in certain beers, although this is not generally a problem to the micro brewer. The presence of calcium reduces colour formation in the copper. This is due to the reduction of extraction of colour forming compounds such as anthocyanogens and pro-anthocyanidins during the sparge.
Calcium ions improve beer fining performance.
Calcium ions encourage yeast flocculation, each divalent positively charged calcium ion attracting negatively charged yeast cells to form small aggregations. With all the above advantages of the presence of calcium and reduction in pH there is one minor disadvantage. The reduction in pH causes a decrease in hop utilisation, giving less bitter beers. This increases hopping costs, since more hops will be required to achieve a desired level of bitterness. You will see that much of the calcium added to the mash is lost - precipitated out as phosphate, proteinate or oxalate.