Blue Print making

Blue Prints were invented by John Herschel, a chemist, astronomer, and photographer, in 1842. Herschel developed the cyanotype process that started with a drawing on semi-transparent paper, weighted down on top of a sheet of paper. The paper was coated with a photosensitive chemical mixture of potassium ferricyanogen and ferric ammonium citrate (a hazardous chemical formula). Once the drawing was exposed to light, the exposed parts turned blue, while the drawing lines blocked the coated paper from exposure and remained white.

The blueprint process eliminated the cumbersome expense of hand-tracing original drawings. By the 1890s in architectural offices, a blueprint was one-tenth the cost of a hand-traced reproduction and could be copied in a fraction of the time using the photochemical process.

Cyanotype is a photographic printing process that produces a cyan-blue print. You can safely replicate this process with Cyanotype solutions like what I have here. (Also known as Sun Prints) The image can be printed on any surface capable of soaking up the iron solution.

Some are more successful than others. 3 to 5 minute exposures are the best.

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