What is Isinglass?


From A Dictionary of Photography, London, 1867:

Isinglass. Fish glue; a pure form of gelatine. It is soluble in boiling water, and gelatinizes on cooling; it is also soluble in weak acids but is precipitated by the addition of an alkali.

Isinglass is obtained from the air bladders of sturgeons, and principally from the great sturgeons found in the Caspian Sea. It is manufactured chiefly at Astracan, and is bleached by the fumes of burning sulphur.

The process of manufacture consists in first steeping the bladders in water, then removing the outer skin, putting them into a hempen bag, squeezing them, softening them between the hands and twisting them into small cylinders, which are afterwards beat into the shape of a lyre.


A philosophical apparatus


I’ve never thought of a camera as a ‘philosophical apparatus’, but the word philosophy means ‘love of wisdom’ so maybe that applies to some photographers.

This advertisement comes from the 1867 book A Dictionary of Photography. It has some intriguing information about photography only 28 years after the medium was discovered.

The company is Horn & Thornthwaite, a name that might have been made up by comedian Peter Cook. They were a leading supplier in London, Opticians to the Queen, and deeply involved in photographic matters. Thornthwaite helped pay the legal expenses of Martin Laroche whom Fox Talbot had sued for his use of the new Collodion process. Talbot claimed that it infringed his Calotype patent of 1839 but he lost the case.

Note that lenses were not described by their focal length, as today, but for plate size. Quarto, half-quarto and Carte, for the Carte-de-Visite format which was all the rage.

One lens costs £6.6s, a large sum for most people. It was four months wages of a servant, for example, which shows photography was a plaything of the wealthy in those days.

A ‘Quire’ is four sheets of paper folded to make 24 sheets. It doesn’t say what size but at that rate, a single sheet of albumen printing paper would be about three pence. That’s about the price of a bottle of beer in 1867 (according to this remarkable website).  If the size is about 10×8 inches, it suggests the price of darkroom paper today is cheaper by half.