Irish moss is the
common name for a variety of red
seaweed. In addition to the uses mentioned in the above write-ups, one species,
Chondus crispus is used in the art of
homebrewing. Added to the
wort in the last fifteen minutes of the boil, the Irish moss bonds to long
protein molecules, effectively removing them from solution. These protein molecules are necessary in small quantities as nutrients for the
yeast, but in larger quantities, this can produce haze in the finished beer.
Irish moss does not effect the flavor of the beer at all. If you forget it, don't worry, clarity is an aesthetic quality of beer, and the real point is to drink it.