Changes
From BrewWiki
German Brewers of old employed an acid rest to acidify the mash, as, due to insufficient calcium ions in the low mineral content water, the mash would not reach the desired pH. The acid rest allowed enzymatic phytase activity and in no small part bacterial activity and growth to acidify mash. The low mineral content water in Dublin was overcome by the addition of highly roasted acid malts and of course made beer quite dark!. Burton water that is high in calcium ions meant that an acid rest was not needed and a single infusion mash is all that was required. Malting technology in the past meant that a percentage of the kilned malt was burnt producing the acidity required such malt was also often poorly modified. Better technology lead to lighter kilned malts great for light lager, but required an acid rest in low calcium waters.
===Water adjusting goals===
When thinking of water chemistry for brewing there are 2 seperate considerations. Firstly, and most importantly, that the dissloved ion profile (mostly Ca ions) be condusive to attaining the correct mash pH in the range of 5.2-5.6. Secondly that dissolved ion concentrations A. Not have a negative flavour impact and B. Where required have a positive or desired flavour contribution. It is no point obsessing over the optimal Sulphate to Chloride ion ratio if excessive tannins are extracted due to a high pH mash!
===Adjusting Water===
