Calcium Sulphate is an adjunct salt and excellent source of calcium ions. Generally used in the brewing of British pales ales and bitters. Treatment allows you to harden your water when mash brewing, as well as lower your wort PH.
Treatment with this adjunct salt causes permanent hardness because it doesn’t get removed by boiling. It is commonly believed that this brewing salt suppresses harsh and astringent flavours. It is further believed that this allows brewers to use larger hop amounts without adding unwanted harsh flavours. However, overuse of this adjunct can produce its own harsh flavours and impact other aspects of your brew.