Irish moss. A reddish-purple seaweed, sun bleached out to a yellowish-pink. Grows in fan-like branches and fronds around Atlantic coasts in the United States and Europe. In its natural state it is tough and almost translucent. Widely used for gelling properties in Ireland where it is, for example, cooked in milk which is then strained to make a set blancmange mould. Can also be used for thickener for soups and stews.