b. 1684; d.1744
Schulze was a German Professor at the University of Altdorf, whose experiments paved the way towards photography. Though it was known that certain chemicals darken when exposed to the sun, it was not clear whether it was the action of light or heat which had this effect. In 1727 Schulze heated some silver nitrate in an oven, and discovering that it did not darken was able to eliminate heat as the darkening agent. Having noticed that a glass jar containing a particular chemical mixture changed colour on one side - that facing the window, he applied paper stencils to a bottle containing silver nitrate and chalk, discovering that where the substance was not exposed to light it remained white. He published details of his investigations, but these did not become popular until after he had died. He described his experiments thus:
I covered the glass with dark material, exposing a little part for the free entry of light. Thus I often wrote names and whole sentences on paper and carefully cut away the inked parts with a sharp knife. I struck the paper thus perforated on the glass wikth wax. It was not long before the sun's rays, where they hit the glass through the cut-out parts of the paper, wrote each word or sentence on the chalk precipitate so exactly and distinctly that many who were curious about the experiment but ignorant of its nature took occasion to attribute the thing to some sort of trick."
© Robert Leggat, 2002.