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what exactly is a blueprint? If you've ever watched a house being built, or if you've ever had an addition put onto an existing house, you know that the standard method of communication is a big piece of paper called a blueprint. Blueprinting is a way to copy large architectural and construction drawings. A blueprint used to consist of white lines on a blue background. More recent processes use blue
lines on a white background. The term blueprint is usually used to describe two printing methods, the blueprint and the diaze type. Blueprinting is the older method, invented in eighteen forty two. The drawing to be copied drawn on translucent paper is placed against paper sensitized with a mixture of ferric ammonium citrate and potassium ferricyanide. The sensitized paper is then exposed a light where the areas of the sensitized paper are not obscured by the drawing. The light makes
the two chemicals react to form blue. The exposed paper is then washed in water. This produces a negative image, with the drawing appearing in white against a dark blue background. In the diaze type method, the paper is light sensitized with a mixture of diazonium salt used in the manufacture of dyes, a reactant, and an acid that keeps the
salt and the reactant from reacting with each other. The semi transparent original is placed on top of this sensitized paper, and a copy of the same size as the original is made by direct contact. Light destroys the salt. Ammonia is used to develop after the exposure. It neutralizes the acid and allows the remaining salt to combine with the reactant to form the blue dye. The chemicals on the paper acquire color only in the areas not exposed to
the light. This diaze type method produces dark lines on a white background, and it's a popular method used today for reproduction of large format drawings. The reason people still use blueprints is because it's an inexpensive process, but large format printers and copiers are getting cheaper and cheaper, and they'll eventually replace blueprints completely. For more on this and thousands of other topics, is it how staff works dot com.
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