Louis invented a coating that made blueprint paper last up to a year.
2.
At that time, blueprint paper was extremely light-sensitive, and had a very short shelf life.
3.
The often reproduced photographs of him and Susan Weil making silhouette negatives on blueprint paper, Rauschenberg's breakthrough pictures, were for Life magazine in 1951.
4.
Elsa remembered helping her mother develop the photographs in wooden frames which were placed in the sun . " You would lay back half of it to see if it was dark enough and close it up again ", she said . " And we used blueprint paper so all you had to do was wash it with water ."
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