isinglass

noun

Etymology: Apparently from obsolete Dutch huisenblas, from German Hausenblase, from Hausen (“sturgeon of the Huso genus”) + Blase (“bladder”), with alteration after glass.

1. A form of gelatine obtained from the air bladder of the sturgeon and certain other fish, used as an adhesive and as a clarifying agent for wine and beer.

   “Isinglass flummery.—Put six ounces of isinglass into a quart of new milk, sweeten it, set it over the fire, and keep it stirring one way all the time, till it is jellied; pour it into basins, and when cold turn it out; you may put in orange flower water if you like.”

   “Isinglass is a substance well known in commerce, from its employment both in the arts and in domestic economy. It is the purest known form of animal jelly, and is obtained from the swimming bladder of a few kinds of fish, chiefly of the genus Sturgeon, the Acipenser of zoologists. This is indicated by some of its continental names, of which the English is no doubt a corruption;—thus, in German, Isinglass is called Hausenblase, from hausen the great sturgeon, and blase a bladder.”

2. A thin, transparent sheet of mica (probably from its similarity to true isinglass and/or resulting from confusion with the term Muscovy glass for glazing made from mica, but also used for isinglass, which was chiefly produced in the Caspian Sea region of Russia, or Muscovy).

   “TALC. / GENUS I. / ISINGLASS. / VITRUM. / Compoſed of broad, flat, cloſe, poliſhed Plates.”

   “There is a general error prevalent that mica is isinglass, and many times it is spoken of as isinglass, but there is a great difference between the two. Mica is mainly composed of silicate of aluminum, while isinglass is a fish gelatine or glue […]”