Calcium sulphate is more commonly known as Gypsum and is used to alter the water chemistry when making beer or added to sherry musts to lower the pH and increase the sherry bouquet.
Calcium sulphate is one of the principal substances found in the water of Burton-upon-Trent and is required for a number of chemical reaction during the brewing process. Mixing Calcium Sulphate
and Magnesium Sulphate together will make a mixture that when added to a beer will give the character of burton beers. This mixture is usually referred to as Burton Water Crystals.
Calcium sulphate will lower the pH of the mash and can also be added to the mash to give the hops more crispness. This will also increase the water hardness, but as it does not dissolve easily
in water, it may take a while of constant stirring to get it to mix properly.
Adding one teaspoon of gypsum to five gallons of water will raise the calcium level by about 60 ppm and the sulphate level by 130 ppm.