Calcium Sulphate - Gypsum
The addition of Calcium Sulphate to the mash will drop mash pH and add Ca2+ ions and (SO4)2- ions to the water.
Calcium ions in solution contribute to permanent water hardness, assist in the growth of yeast during the lag phase and help to precipitate proteins during the hot break.
Sulphate ions in solution will assist in providing hop bitterness and flavour to beers and influences the sulphate:chloride ratio. Adding sulphate ions to mash water will alter the ratio in mash water which will impact the perceived flavour of the beer. Lower ratios such as 1:2 or 1:3 will highlight malt flavours in beer while higher ratios such as 2:1 or 3:1 will highlight hop bitterness and flavour.