by Robert M. Downie

Free dessert plucked from the beaches.

The following article originally appeared in the Block Island Summer Times, Fall 2006 edition, under the title "Irish Moss Seaweed: Block Island's free dessert." It is reprinted here with permission.

Irish moss, an edible seaweed, can be found easily on Block Island beaches, particularly after storms. The natural deep purplish color will soon bleach out to a lustrous white, as shown here.

In about the year 1850, Block Islanders began gathering Irish moss during the warmer months, a pursuit introduced to them by a mainlander. This purplish seaweed grows from New Jersey northwards into Canada, found clinging to rocks near the shore and easily visible on beaches when washed up by storms. After several days, dead Irish moss bleaches to white, looking a little bit like cauliflower. One hundred to 150 years ago at low tide, when the seaweed could be picked directly from the rocks, Block Islanders—particularly women and children—might be seen gathering this free offering from nature.

Taken home, the seaweed was washed, raked, and dried outdoors in repeated cycles. The whitened result was sold in local stores in bags ranging from five to thirty pounds. When the store accumulated enough, the seaweed was shipped to mainland druggists to be mixed as a thickener in numerous preparations. Or it was sent to woolen and flannel mills in Connecticut for use in a process that strengthened thread. By 1880, 400 barrels (or 24,000 pounds) of processed Irish moss were being shipped off the island annually—a supplemental income to fishing, farming, and the rapidly growing business of tourism.

In 1895, a Boston man contemplated bringing modern equipment to Block Island, to increase tenfold the amount of Irish moss harvested by hand. Nothing came of the proposal and, compared with the best of locations on the mainland, the collection of Irish moss here remained a modest enterprise.

During the decade from 1912 to 1921, William Sharp operated the Block Island Public Market on Dodge Street. The letterhead of his stationery proclaimed "Irish moss" for sale, as well as an eclectic mix of other offerings including "island lambs," poultry, eggs, vegetables, and Ford cars. Islanders who did not care to tramp the beaches would purchase Irish moss to use in the same ways that households on the mainland did: to soothe sore throats, or as the main ingredient for numerous kinds of puddings and jellies.

Carrageen and carrageenan

The two words "carrageen" and "caragheen" are other names for Irish moss, derived from the seaweed-rich village in southeast Ireland called Carragheen. Hence, among ingredients listed on food packages you will seldom see "Irish moss," but you will find listed a third and fourth word based on Ireland's little seaside town—"carrageenan" or "carageenin"—the names for the colloidal substance extracted from Irish moss.

And if you ever read the words Chrondus crispus, that is Irish moss too—the Latin phrase used by biologists to confuse the average person further.

By the 1930s, more than 300 uses of Irish moss had been discovered by industries worldwide, including these:

  • to make smoother-flowing pharmaceutical products such as laxatives, cough syrups, hand lotions, toothpaste, shaving creams, lipstick, and cosmetics;
  • to thicken and stabilize foods such as chocolate milk, ice cream, jellies, puddings, cream cheese, cottage cheese, salad dressings, frozen yogurt, icing, pie fillings, meringues, fountain syrups, gravies, canned meat, and packed fish;
  • to improve the manufacture of products such as mineral oil, shoe polish, tanned leather, soap, glue, adhesives, cloth, thread, water paints, and paper;
  • to clarify beer and create more "body" by lowering screens covered with cured Irish moss into brewing vats.

There was something for everyone!

By then Block Island was no longer a commercial provider of Irish moss. But the seaweed is still harvested extensively along New England's coast north of Cape Cod, and the uses continue. During the mid-1990s, for instance, McDonald's restaurants offered "91 percent fat free" hamburgers called McLean Deluxes—and listed among the ingredients was "carrageenan."

Even if you do not purchase Irish moss, the seaweed is as ubiquitous as ever and will catch up to you. It is already in our bodies because of the foods we eat, as thoroughly as it is scattered along Crescent Beach after a storm. And that, of course, is where you should get it—on almost any Block Island beach. Just look behind the Surf Hotel for starters. You'll usually find the dark purple kind, or the bleached white aftermath, which after washing is ready to be cooked.


To take your Irish moss straight, or as concentrated as can reasonably be expected, make the pudding called blancmange. The word "blanc-manger" in French means literally, "white-to eat"—and in Gallic cooking it is a white pudding made with milk, almonds, sugar, seasonings, and gelatin. The gelatin—which causes liquids to coagulate or gel—is a prepared product made from bones, connective tissue, and the skin of animals.

But in America in the 1800s and early 1900s, blancmange—often spelled then as two words, "blanc mange"—was made without the almonds, and with Irish moss used to thicken the pudding instead of gelatin. Once dried, the moss could be kept for years. In publications such as Fannie Farmer's The Boston Cooking School Cook Book of 1931, and the Yankee Cook Book of 1939, by Imogene Wolcott, blancmange was still made with Irish moss, sometimes called simply "sea moss."

Recipes for blancmange in cookbooks published after World War II usually deleted the Irish moss, and still do, substituting either gelatin or cornstarch as the thickening agent. Do not hesitate to add other suggestions found in old cookbooks, such as cream, vanilla, coconut, berries, sliced bananas, figs, almond flavoring (back to the French version) with or without coffee extract, honey, a pinch of salt, or anything else that seems appropriate.

A Block Island dessert as pure as a fresh sea breeze would be, of course, blancmange with hand-picked blackberries.

Try it yourself

The purest, most elemental recipe based upon Irish moss can be found in the Block Island Cookbook, first published in 1962. This contribution was submitted at that time by Beatrice Ball Dodge and uses, for the pudding itself, merely:

1/3 cup of moss
2 cups of milk

  • Gather fresh moss on the beach.
  • Rinse well in cold water and spread in the sun to dry.
  • When ready to use, soften 1/3 cup of moss by covering it in cold water for fifteen minutes.
  • Drain and add 2 cups of milk.
  • Cook in a double boiler for thirty minutes without stirring.
  • Strain into a bowl or molds, and cool—it thickens only on cooling.

Serve with jam, light flavored cream, boiled custard, chocolate sauce, or fruit, fresh or stewed. The blancmange is rather tasteless by itself and depends on the sauce for flavor.

Historian Robert M. Downie is the author of Block Island: The Land (1999) and Block Island: The Sea (1998). He is a frequent contributor to the Block Island Times.

Bonus Irish Moss Recipes

Moss Blanc-Mange


  • 1 cup of Irish moss
  • 3 quarts of milk
  • 1 teaspoon of salt
  • ½ cup of sugar
  • Flavoring (anything you please)

Wash moss several times to make sure there are no pebbles, sand, or seaweed. Let it soak in cold water at least one hour. Tie in a muslin bag and put in a tin pail with three quarts of milk. Set the pail in another large pan of hot water and boil thirty minutes. When it comes to a boil, stir occasionally. Press the bag between the side of the pail with a spoon to get out all of the gluten; remove the bag, stir in a teaspoonful of salt, half a cup of sugar, and flavoring. Pour into individual dessert cups and let cool. Serve with sugar and cream.

—from The Griddle: A Bicentennial Cook Book of Washington County Receipts, compiled by the volunteers of the Jonnycake Center, Inc., (1976).

Irish Moss Lemonade

Alice Johnson (old family recipe)

  • ¼ cup of Irish moss
  • 4 tablespoons of lemon juice
  • sugar (to taste, about 3 tablespoons)
  • 2 cups of boiling water

Wash, pick over and soak the moss one half hour. Pour off the water and add boiling water. Cook, but not boil, until it becomes syrupy. If it becomes too thick add more water. Strain, then add lemon juice and sugar to taste. Serve hot. This is excellent for sore throats and cold on the lungs, or any inflammation of the mucus membranes.

—from The Griddle: A Bicentennial Cook Book of Washington County Receipts, compiled by the volunteers of the Jonnycake Center, Inc., (1976).

This article last edited September 3, 2015

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