When you look through beer recipes you may notice an ingredient called “Irish Moss.” If you are not familiar with it you may wonder why you would add such a thing to your beer.
Irish Moss is actually derived from a type of seaweed that is mostly found near Ireland. It is used to help produce a more clear beer. While some beer styles, such as wheat beers, are supposed to have some haze to them, most are not. For home brewers, though, haze is fairly common. This haze is usually caused by proteins in the beer that clump up, especially when the beer is cooled, thus it is known as “chill haze.”
When you are brewing beer you can prevent chill haze and overall haziness by cooling the wort very rapidly after the boil. This is usually accomplished using a wort chiller, which you can find at your local home brewing store. An ice bath will not usually cool beer quickly enough. The rapid cooling causes what is known as the “cold break,” where many of the proteins flocculate, or clump up, and settle out of the wort.
In addition to rapidly cooling the wort, haze can also be prevented by adding a “fining agent,” or a substance that causes proteins to flocculate. Irish Moss is a substance that will do this. One teaspoon of Irish Moss is added for every five gallons of wort fifteen minutes prior to the end of the boil. Irish Moss can be found at just about any home brewing supply store.
An alternative to Irish Moss is a Whirlfloc tablet. These tablets are an enhanced form of Irish Moss and a substance called carrageenan, which is derived from red seaweed. These tablets come in an easier-to-measure form (one tablet for ten gallons, half a tablets for five gallons) and are added just five minutes before the end of the brew (if they are in the wort for more than ten minutes they will actually not work as well).