Encyclopedia > Blueprint

  Article Content

Blueprint

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Blueprints have mostly been replaced by Diazo prints or whiteprints, which have blue lines on a white background.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

... size is 3.04. In the town the population is spread out with 25.2% under the age of 18, 4.8% from 18 to 24, 27.3% from 25 to 44, 28.7% from 45 to 64, and 13.9% who are 65 ...

 
 
 
This page was created in 30.5 ms