![]() ![]() ![]() Xerography is standard copy machine technology using toner on bond paper. To this day, they are still often called “blueprints.” Other comparable dye-based prints were known as “blacklines.”ĭiazo prints remained in use until they were replaced by xerographic print processes. For decades, bluelines were the way to make copies of engineering drawings. Moreover, the machines needed to make them were not overly expensive for reprographic companies and didn’t need extensive maintenance. They were easier to read and faster to make than the original blueprints were. In the 1940s, blueprints were replaced by diazo prints, aka “whiteprints” or “bluelines.” Diazo prints had blue lines on a white background. The resulting image was therefore appropriately named “blueprint.” Where Have all the Blueprints Gone?īy the 1890s, architectural firms found that blueprints were one-tenth of the cost of hand-traced reproductions and could be copied in a fraction of the time via the photochemical process developed by Herschel. After the paper was washed and dried to keep those lines from exposing, the result was a negative image of white (or whatever color the blueprint paper originally was) against a dark blue background. When the two papers were exposed to light, the two chemicals reacted 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 was blocked by the lines of the original drawing. The drawing was then placed over another piece of paper, which was coated with a mix of ammonium iron citrate and potassium ferrocyanide (from an aqueous solution and then dried). The cyanotype process started with a drawing on semi-transparent paper that was weighted down on top of a sheet of paper. It also allowed rapid and accurate production of an unlimited number of copies of drawings. Herschel’s cyanotype blueprint process eliminated the cumbersomeness and expense of hand tracing original drawings. The first blueprint was developed in 1842 by John Herschel, an American chemist, astronomer and photographer. ![]() Have you ever wondered why blueprints are called blueprints? The answer is surprisingly simple. ![]()
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