Isinglass

Isinglass (/ˈaɪzɪŋɡlæs/ or /ˈaɪzɪŋɡlɑːs/) is a substance obtained from the dried swim bladders of fish. It is a form of collagen used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes.

Its origin is from the obsolete Dutch huizenblaas – huizen is a kind of sturgeon, and blaas is a bladder. Isinglass is no longer sourced from sturgeon.

Although originally made exclusively from sturgeon, especially beluga, in 1795 an invention by William Murdoch facilitated a cheap substitute using cod. This was extensively used in Britain in place of Russian isinglass. The bladders, once removed from the fish, processed, and dried, are formed into various shapes for use.

Before the inexpensive production of gelatin and other competing products, isinglass was used in confectionery and desserts such as fruit jelly and blancmange.

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