Encyclopedia > Blueprint

  Article Content


A blueprint is a photographic print composed of white lines on a blue background. Blueprints were commonly used in the past for copying architectural plans and engineering drawings.

The blueprint process was developed by the British astronomer Sir John Herschel in 1840. The photosensitive compound, a solution of ammonium ferric citrate and potassium ferricyanide, is coated onto blueprint paper. Areas of the compound exposed to strong light are converted to insoluble blue ferric ferrocyanide, or Prussian blue. The soluble chemicals are washed off with water leaving a light-stable print.

Blueprints have mostly been replaced by Diazo prints or whiteprints, which have blue lines on a white background. These are sometimes also known, incorrectly, as blueprints.

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article
Northwest Harbor, New York

... age or older. The average household size is 2.59 and the average family size is 3.04. In the town the population is spread out with 25.2% under the age of 18, 4.8% from 18 ...

This page was created in 33.5 ms