Diazo machines have been around a long time. Navy shops still have these
workhorses tucked away in reproduction rooms. Although diminished in
importance, these machines continue to produce good quality, cost effective,
correctable reproductions on paper, Mylar, vellum, and acetate foils.
Two general systems are in use in diazo process machines. The first is a
continuous gravity feed ammonia system. These machines drop ammonia at
the rate of 50 to 60 drops per minute into a tray where heater rods vaporize
the ammonia into developing fumes. The second type of diazo system is the
anhydrous ammonia system that mixes ammonia vapor with distilled water.
Figure 4-2 illustrates ammonia vapor production in a gravity feed and an
Figure 4-2. Ammonia vapor production.
Continued on next page