January 9, 1839. Long before cell phone cameras, people took photos using copper and heat. On this date, the French Academy of Sciences announced Louis-Jacques-Mandé Daguerre’s daguerreotype photography process to the world.
Exposure times for early daguerreotypes were typically about 10 minutes, with pictures taken on a sheet of copper that had a coat of silver halide on top. After exposing the sheet to heat, the plate would be treated with substances to bring out the image.
Although painfully slow by today’s standards, the relatively rapid processing time made commercial photography a viable business for the first time. Reports indicate it took only about half an hour to develop images. It used to take hours before that.