Diazo copier

A diazo copier,[1] whiteprint copier or blue-line copier, is a type of heliographic copier used in the world of reprography for making positive contact prints on paper from original drawings made on vellum or other transparent or translucent material using the diazotype technology.

The different names were given, due to the nature of the process, which consists in exposing to an ultraviolet light a previously sensitized paper with a component called diazo, and finally developing it in a bath (a solution of ammonia in water) which converts the parts not exposed to light, to a dark blue colour (blue-line) on an almost white background.

History

The light sensitivity of certain chemicals used in this process, it was already known in the 1890s and several related printing processes were patented at that time. The process of diazotype replaced the cyanotype process for reproduction of drawings of architectural and engineering blueprints, because the technique was simpler and made use of less toxic chemicals.[2]

In the "argot" of engineers, architects and designers, no matter they were either blue or white, the resulting plan copies were traditionally called blueprints, name derived from the blue background color of the cyanotype technique, which was the previous process for obtaining blueprints. When the diazo based compounds changed the background color to white, in technical environments, -by tradition-, the name for copies of technical drawings remained Blueprint , although in English-speaking countries, it was intended, without much success, to change the name from Blueprint to Whiteprint .[3]

Operation

Diazo copies of drawings

The original plan and the sensitized paper , are introduced, in perfect contact, within the copier rollers that pull and expose them to a source of ultraviolet light, typically a blacklight lamp, similar to the manual action to expose both sheets strongly bonded directly to the sunlight.

Once exposed the copied paper is immersed in a developer solution made from ammonia (or ammonia vapor) converting in the parts of the paper not exposed to the light source to a characteristic dark blue colour .

Features

A little smell of ammonia and a faintly purplish paper colour are the main characteristics of a whiteprint. The dark lines in the original are converted to a dark violet colour, while the white parts degrade to a light purplish colour. The back of the drawings is a cream colour in which the folds are degraded to a lighter colour.

The diazo copies are of different sizes and for this reason the diazo paper is obtainable in standard sizes that vary from 30 cm to 60 cm wide, after de process the copied paper can be cut to the desired size.

The paper used for the diazo copies is usually a bond paper or similar type, with a diazo coating sensitive to the UV light.

See also

References

  1. ↑ FJM Wijnekus; E.F.P.H. Wijnekus (22 October 2013). Dictionary of the Printing and Allied Industries: In Inglés (with definitions), French, German, Dutch, Spanish andItalian. Elsevier Science. pp. 844 –. ISBN 978-1-4832-8984-7.
  2. ↑ Blueprints replaced by whiteprints
  3. ↑ David L. Taylor (2004). Blueprint Reading for MachineTrades. Cengage Learning. pp. 3 –. ISBN 1-4018-9998-6.

External links

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