Pure Coarse Ground Irish Moss or Copper Finings. Irish Moss is a clarifier and is used to clear protein during the boil when mash brewing. It is a seaweed derived fining agent used by many brewers to help make a clear beer without the need for a filter, and to prevent chill haze. Irish Moss accelerates protein coagulation during the end of the boil which helps to prevent chill haze. Add one teaspoon per 20L of wort, 10 minutes before the end of the boil. Was Copper Tun previously.