Blueprints celebrate two things we love: our natural curiosity about how things are made and gorgeous design. From iconic buildings to engineering marvels and maps of landmark cities, blueprint art is eye-candy for the designer in all of us.
Taken from Mental Floss … The blueprinting process was developed in the mid-1800s, when scientists discovered that ammonium iron citrate and potassium ferrocyanide created a photosensitive solution that could be used for reproducing documents.
The process goes like this: Someone creates a drawing on translucent tracing paper or cloth. The drawing is placed over a piece of blueprinting paper, which has been coated with a mix of ammonium iron citrate and potassium ferrocyanide from an aqueous solution and dried. When the two papers are exposed to a bright light, the two chemicals react to form an insoluble blue compound called blue ferric ferrocyanide (also known as Prussian Blue), except where the blueprinting paper was covered, and the light blocked, by the lines of the original drawing.