Diazotypy , diazography is a non-silver photographic process based on the photosensitivity of diazonium salts , which are destroyed by light [1] . The diazo process is directly positive, that is, a positive is immediately obtained from a positive image. Diazotypic photographic materials have low sensitivity and do not reproduce a halftone image poorly, therefore they are widely used for copying documentation. With the spread of photocopying, diazotype has almost completely been squeezed out of the workflow market, but continues to be used to apply logos on metal surfaces.
Content
Technology Description
The first diazo photo paper for the blue print was released in Germany in 1923 [1] . Diazo photo materials can be of three types: with a wet (one-component) or dry (two-component) manifestation , and also manifested by heating [2] . In the latter case, the photographic material contains all the components necessary for the manifestation in the photosensitive layer, and the visible image appears after heating to 180 ° C. This type is called thermal diazo paper [3] . The original, made on a translucent tracing paper , is placed between the light source and the carrier (diazo-paper) on which contact printing is performed. The copying process is carried out in special frames or light-blueprints with powerful mercury-quartz ultraviolet lamps .
Exposed two-component diazo paper with dry development is treated in fume cupboards with ammonia vapor. Unicomponent diazo papers are manifested by a wet method by applying an alkaline solution of a mixture of azo-components with a special capillary roll [3] . In areas not exposed to light, azo dyes are formed during the development process. The resulting copy of the drawing in the everyday speech of engineers, architects and draftsmen was called blue , obtained due to the background color of the previous technical process version, cyanotype . When chemical processes were later changed and the background color changed, the name blue remained in Russia as a tradition, although in English-speaking countries the name changed from Blueprint to Whiteprint .
See also
- Vesicular process
- Cyanotype
Notes
- ↑ 1 2 Photokinotechnology, 1981 , p. 76.
- ↑ General course of photography, 1987 , p. 228.
- ↑ 1 2 Science and Life, 1991 , p. 64.
Literature
- E. A. Iofis . Photo kinotekhnika / I. Yu. Shebalin. - M.,: “Soviet Encyclopedia”, 1981. - p. 76. - 447 p.
- A. Fomin § 2. The diazo-type process // General Photography Course / T. P. Buldakova. - 3rd. - M.,: "Legprombytizdat", 1987. - p. 228-229. - 256 s. - 50 000 copies
- G. Zatikyan. Prospects for diazography // Science and Life : Journal. - M .: True, 1991. - № 2 . - pp . 63-64 . - ISSN 0028-1263 .