The salt print was the dominant paper-based photographic process for producing positive prints (from negatives) from 1839 until approximately 1860.

The salted paper technique was created in the mid-1830s by English scientist and inventor Henry Fox Talbot. He made what he called "sensitive paper" for "photogenic drawing" by wetting a sheet of writing paper with a weak solution of ordinary table salt (sodium chloride), blotting and drying it, then brushing one side with a strong solution of silver nitrate. This produced a tenacious coating of silver chloride in an especially light-sensitive chemical condition. The paper darkened where it was exposed to light. When the darkening was judged to be sufficient, the exposure was ended and the result was stabilized by applying a strong solution of salt, which altered the chemical balance and made the paper only slightly sensitive to additional exposure. (Wikipedia)


In ONE LAST HOUR, I skip this last step, in order to keep the light sensitivity of the prints.

This evanescent trace of a biological specimen, (see picture) among the rarest of photographs, was made by William Henry Fox Talbot just months after he first presented his invention, photography—or "photogenic drawing," as he called it—to the public. Plants were often the subject of Talbot's early photographs, for he was a serious amateur botanist and envisioned the accurate recording of specimens as an important application of his invention. The "Album di disegni fotogenici," in which this print appears, contains thirty-six images sent by Talbot to the Italian botanist Antonio Bertoloni in 1839–40. It was the first important photographic work purchased by the Metropolitan Museum.


Photographs and herbarium specimens are tools to define the extinction of plants.

In ONE LAST HOUR each extinct plant is conserved through a salt print. By opening the Box, the contact with the light let the photograph disappear. The different concentration of salt and silver nitrate makes the different colours in the prints

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