The uses of carageen (Irish Moss) in manufactures make it an article of some importance; and the present high price of glue and isinglass, for which it is an excellent substitute, has created a demand for it, heretofore unknown. It is also cheaper than eggs for clearing coffee. Up to the year 1848, all the carageen used in the United States was imported from Ireland. It was collected on the southern and western shores of that Island. In 1849 several parties commenced making a business of gathering and curing Chondrus Crispus Scituate Plymouth Co. Massachusetts and produced the first considerable quantity of the domestic article ever sold in Boston.
This is still the only point in the United States where any noticeable amount is collected and the annual crop is not far from 500,000 pounds, equal to about 6,000 barrels. It's most important use is for sizing; it being used for the manufacture of cloth, paper, and felt, and straw hats. The poor qualities are bought up for size. The hand-pulled moss, however, contains more starchy matter than the variety which is never exposed to the air. The second quality of moss is sold to the brewers. All beers, when well brewed and sound, after a certain repose, become transparent. When, however, beer is sent out very new, it is necessary to 'fine' it or impart to it its transparency.
This is done by means of finings. In Europe, isinglass, is used for this purpose, and a lengthy formula is given for its preparation; but in this Country (US) Irish Moss performs the same service without any preparation other than that given it by the curer.
Transcription from the Manufacturer and builder Vol 1 Issue 4 published by Western and Company of New York City in Apr 1869