isinglass

noun

1. (uncountable, usually)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.”

   “Isinglass.—This is procured from the air-bag or swimming-bladder, sometimes termed the sound, of various fishes. […] Sometimes the bag is dried unopened, as in the case of the purse, pipe, and lump isinglasses of the shops. At other times it is laid open, and submitted to some preparation; being either dried unfolded, as in the leaf and honeycomb isinglasses; or folded, as in the staple (long and short) and book isinglasses; or rolled out, as in the ribbon isinglass.”

2. (uncountable, usually)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 […]”

   “MICA (ISINGLASS). Mica is valuable because of its perfect cleavage, transparency, elasticity, non-conductivity of heat and electricity, resistance to decomposition, and non-inflammability. It is mostly used as an insulating material in the manufacture of electrical apparatus.”

   “The dashboard's genuine leather, / With isinglass curtains y' can roll right down, / In case there's a change in the weather.”

   “THE FRONT DOORS OF MY STOVE HAD WINDOWS of isinglass (mica) which needed replacement. While impervious to heat, isinglass is quite fragile and one must avoid touching these panels when using the doors. The panels are held in place by a frame bracket screwed to the inside of each door. Fortunately, a supply of extra mica panels was found in the house.”