Blueprints

Blueprints are an essential part of the manufacturing process.  Products can't be made until they've been designed and properly planned, and blueprints are the technical drawings needed to make those ideas a reality.  

In 1842, British astronomer and photographer Sir John Herschel developed the cyanotype process, which is effectively the same method used to create early blueprints.  In cyanotype, an 8% solution of potassium ferricyanide and a 20% solution of ferric ammoniumis were mixed together, creating a photosensitive solution capable of being applied to paper.  When exposed to ultraviolet light, the areas covered with the solution turned a Prussian blue color.  The remaining chemicals were then washed off with water, creating a stable print.  

In the early days of manufacturing, blueprints were the easiest, most cost effective way of producing copies of plans.  As soon as the process was invented, it immediately became a fixture of the manufacturing process.  

The way it worked was simple.  The technical drawing was made with India ink on a tracing paper.  The tracing would be placed over the paper covered with the photosensitive solution, and both would then be loaded into a wood frame and placed outside in the sun.  Once the bottom page turned blue, it would be removed from the frame and washed with water.  The result would be a reproduction of white lines on a blue background that was incredibly resistant to light and water damage.  Modern technologies have since rendered the original blueprinting process obsolete, but it remains an important part of manufacturing history.