What is Carrageenan?

I have a recipe for a bath jelly, which includes gelatin to make it into a semi solid state like jello. But there are vegans out there who do not use this type of ingredient in their everyday lifes. So I was wondering what I could replace the gelatin with. I have heard of agar. I have not tried agar or Carrageenan? What is Carrageenan? According to Wisegeek.com:

"Carrageenan comes from algae or seaweed, and can be used as a thickening agent in place of animal-based products like gelatin, which is extracted from animal bones. It is usually derived from either red alga, sometimes called Irish moss. Carrageenan is a common ingredient in many foods, such as milk products like yogurt or chocolate milk.

One can make one’s own carrageenan by boiling down Irish moss for about 20 to 30 minutes. When the mixture cools, and the moss is removed, one is left with a gelled substance. Since many recipes call for a thickening agent, many vegetarians use carrageenan in place of products like gelatin, since it is 100% vegetarian.

One can often purchase powdered carrageenan at natural food stores. It may be used in the preparation of certain wines and beers. Also many sliced deli meats are enriched with carrageenan. Carrageenan may also be marketed in its jelled form as a personal lubricant. Companies like Tom’s of Maine® use carrageenan in a variety of products from toothpaste to deodorant.

Some use carrageenan to make foods like vegetarian marshmallows, to gel jelly, or stabilize ice cream. As it cooks, it often has a fish like odor. This odor and taste is usually masked by the foods in which it is used. Carrageenan in algae form is also quite rich in iron and sulfur. However, when it is processed into a gel, it usually looses these minerals.

Carrageenan is also equivalent to agar, which is derived from red algae, and sometimes seaweed. The process is the same for producing agar as it is for making carrageenan. In both instances, the alga is boiled down to make a jelly substance.

Agar is used as a culture for bacteria in medicine and microbiology. Its gel-like substance is the perfect place to grow bacteria or to test for bacterial presence. Some also use agar as medicine, since it tends to produce a laxative effect.

Like carrageenan, agar may be used in ice cream, soup, jelly, or in brewing wine or beer. It also is a vegetarian alternative to gelatin. In fact, since virtually no difference exists between the two substances, they are excellent substitutes for each other. It is more common in Asian countries to see agar listed as a thickening agent, while in the US, the term carrageenan is more commonly used."