Viewgraphs, Continued
Diazo
Making a viewgraph with the diazo process involves using specially treated
films and papers and a diazo printer. Diazo film, foils, and paper treated
with a mixture of diazo salts and azo dyestuff form images in colors and
black. The salts are light sensitive. After you expose a foil to a light source,
particularly an ultraviolet light, develop it in an alkaline medium, such as the
vapors of commercial ammonia (ammonia hydroxide) with a reading of 26°
Baumè. The salts combine with the azo dyestuff during the development
process to leave an image. Exposure time in the printer is critical, develop
only long enough to obtain maximum color saturation.
Figure 2-22 shows the diazo process simplified.
Figure 2-22. —The diazo process simplified.
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