red since both block the ultraviolet light effectively. Opaque tapes are available in various sizes ranging
from 1/16 inch and up. These tapes are very useful for line work on film.
Once you have completed preparing your master, you are ready to transfer it to diazo film. You transfer
the master chemically, using a diazo processing machine.
5. Diazo Processing Equipment.
Several companies manufacture diazo processing equipment. The major difference between machines is
the size of materials they accommodate. There are four major sections to diazo machines: printing,
developing, cooling, and exhaust.
a. Printing Section. The printing section consists of four basic units: light source, reflector
assembly, print cylinder, and feed belts. Figure 2-5 shows the basic operation of the printing and the
developing sections.
(1) For the reproduction process, you insert the original (master) and the diazo material into
the machine.
(a) You place the diazo material emulsion side up on the freeboard, with the original
placed on top. The feedbelts carry the materials around the revolving print cylinder, exposing the diazo
material.
(b) After exposure, the pick-off assembly picks off the original and the print, and directs
them toward the developing section.
(2) After the pick-off, the guide roller directs the original and the print to the separation
tanks. This assembly separates the original and the print. The original moves out of the machine and
the print moves to the developing section.
b. Developing Section. The developing section consists of a perforated stainless steel tank and a
feed system. A supply tank continuously feeds the developing tank with ammonia at a rate of 50-60
drops per minute.
Electric heating rods in the developing tank heat the ammonia to accelerate the formation of ammonia
vapors. These vapors escape through the perforations of the tank, and activate the image on the print.
Figure 2-6 illustrates a basic ammonia flow system.
2-10
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