What is a heliotype?

73 rue Claude Bernard, Paris / via Google Maps

73, rue Claude-Bernard, Paris / via Google Maps

Heliotype E. Le Deley, Paris

Héliotypie E. Le Deley, Paris

The heliotype was invented by Ernest Edwards (1837-1903), who later outlined the process in his book, The Heliotype Process (Boston: James R. Osgood & Co, 1876). Though earlier begun by others, it was Edwards who perfected the process in about 1870.

The Merriam-Webster dictionary defines a heliotype as a “photomechanically produced plate for pictures or type made by exposing a gelatin film under a negative, hardening it with chrome alum, and printing directly from it.”

The David A. Hanson Collection of the History of Photomechanical Reproduction presents scans of Ernest Edwards’ The Heliotype Process in its entirety here. (You can also read it on Google Books.)

In American Library Edition Of Workshop Receipts Vol 2 (Spon & Chamberlain, 1903), Ernest Spon explains the process of creating a heliotype:

(32) Heliotype

The most important of the many modifications of the collotype process is the “heliotype” invented by Ernest Edwards, wherein the great advantage consists in toughening the gelatine film by means of chrome-alum. His method is briefly as follows:

The solution of gelatine and bichromate, with the due proportion of chrome-alum, is poured upon the previously waxed surface of a carefully levelled glass plate, and dried, when the film is readily detached. The latter resembles a piece of thick paper, and may be similarly handled. After exposure in contact with a negative, the film is placed on a plate of zinc or pewter under water, and firmly attached by passing an india rubber “squeegee” sharply over the surface of the film.

The printing film on its plate is soaked in water sufficiently long to remove the superfluous bichromate, to prevent the further action of the light, and is then ready for the press. This is preferably on the vertical principle, such as the Albion printing – press.

The inking possesses peculiar features; a very stiff ink may be used to give the deepest shadows, and this may be followed by a thinner ink, even one more or less coloured, for the half-tones, thus producing a bichromatic effect in a single printing.

The time occupied in drying the film is 24 to 36 hours at 90° F. (32° C.); 1500 copies have been successfully taken from one plate; one man can print 200 to 300 copies daily; for very long numbers, it can hardly compete with lithography in price, but for moderate numbers the cost is very small.

(Read more at chestofbooks.com.)

Writing in the journal Nature‘s June 1 1871 issue, William H. Harris gives a lengthier, very detailed report, which the University of Wisconsin has transcribed online. Read it here.

The process is also discussed in the book Darwin’s Camera: Art and Photography in the Theory of Evolution by Philip Prodger.

E. Le Deley

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As for the printer, E. Le Deley, information is scarce. He is known to have printed many images for books and portfolios, including other work for Armand Guerinet.

However the postcard website, , has some information which identifies E. Le Deley as having been a prolific printer of postcards. It states that the Le Deley company was family-run, and went out of business in 1930.

In 1905 (and perhaps before), E. Le Deley was located at 73, rue Claude-Bernard in Paris. The building still exists today. (See photo at top of the page.)

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