During the first half of the 19th century, many photosensitive metal salts had been identified as candidates for photographic processes, among them uranyl nitrate. The prints thus produced were called uranium prints or uranotypes. The first uranium printing processes were invented by Scotsman J. Charles Burnett between 1855 and 1857, and used this compound as the sensitive salt. Burnett authored a 1858 article comparing « Printing by the Salts of the Uranic and Ferric Oxides » The process employs the ability of the uranyl ion to pick up two electrons and reduce to the lower oxidation state of uranium(IV) under ultraviolet light. Uranotypes can vary from print to print from a more neutral, brown russet to strong Bartolozzi red, with a very long tone grade. Surviving prints are slightly radioactive, a property which serves as a means of non-destructively identifying them. Several other more elaborate photographic processes employing the compound appeared and vanished during the second half of the 19th century with names like Wothlytype, Mercuro-Uranotype and the Auro-Uranium process. Uranium papers were manufactured commercially at least until the end of the 19th century, vanishing due to the superior sensitivity and practical advantages of silver halides.

https://en.wikipedia.org/wiki/Uranyl_nitrate#Archaic_photography

Au cours de la première moitié du XIXe siècle, de nombreux sels métalliques photosensibles ont été identifiés comme candidats aux procédés photographiques , parmi lesquels le nitrate d’uranyle. Les empreintes ainsi produites étaient appelées empreintes à l’uranium ou uranotypes. Les premiers procédés d’impression à l’uranium ont été inventés par Scotsman J. Charles Burnett entre 1855 et 1857, et utilisaient ce composé comme sel sensible. Burnett écrit un 1858 article comparant « Impression par les sels des uranic et ferrique Oxyde » Le procédé utilise la capacité de l’ion uranyle pour ramasser deux électrons et de réduire à la plus faible état d’oxydation de l’ uranium (IV) sous ultraviolet de la lumière. Les uranotypes peuvent varier d’un imprimé à l’autre, d’un brun roux plus neutre au rouge Bartolozzi fort , avec un degré de tonalité très long. Les empreintes survivantes sont légèrement radioactives , une propriété qui permet de les identifier de manière non destructive. Plusieurs autres procédés photographiques plus élaborés utilisant le composé sont apparus et ont disparu au cours de la seconde moitié du XIXe siècle avec des noms tels que Wothlytype, Mercuro-Uranotype et le procédé Auro-Uranium. Les papiers d’uranium ont été fabriqués commercialement au moins jusqu’à la fin du 19ème siècle, disparaissant en raison de la sensibilité supérieure et des avantages pratiques des halogénures d’argent.

https://stringfixer.com/fr/Uranium_nitrate

Shot Able took place June 30, 1946 at Bikini in the Pacific. It was the first of the two atomic tests that constituted Operation Crossroads. The detonation occurred just above the surface of the lagoon, and the yield was nominal, ca. 21 kilotons.

This print of Shot Able, produced in 2004 by Blake Ferris, is a uranotype (approximately 4″  x  8″).

During the infancy of photography in the mid 1800s, a variety of light sensitive metallic salts were investigated for use in producing photographic images. While the silver halides would ultimately prove to be the best, salts of platinum and uranium were, for a time at least, widely employed.

The first use of uranium in photography is credited to J. Charles Burnett who in the 1850s employed uranyl nitrate as the photosensitive salt.

The process for producing a uranotype is more or less as follows:

• First, the paper is sensitized by soaking it in a solution of uranyl nitrate and allowing it to dry.
• Next, the negative (high contrast) is placed in contact with the paper and exposed to ultraviolet light.
• Finally, the exposed print is developed in a ferrocyanide solution and washed. The resulting reddish image is due to the formation of uranyl ferrocyanide.

Note that the image in a uranotype is produced by uranium. This is different from the situation wherein uranium is used as a toner to alter the image created by another metallic salt (e.g., silver bromide).

The surface activity of the accompanying photo is approximately 900 cpm above background as measured with a pancake GM probe. A radioactive plume.

The following are examples of the various formulae for the sensitizer and developer used to produce uranotypes.

• Sensitizer – 4 grams of uranium nitrate in 16 mls of water
• Developer – 10 grams of potassium ferricyanide in 300 mls of water

Photo donated by Blake Ferris.

https://www.orau.org/health-physics-museum/collection/miscellaneous/uranotype.html