The exposure and development of diazo foils and papers are by trial and
error. The variables that effect exposure and development are the
translucency of the master, the color foil selected, the age of the foil, the
intensity of the light source, and the degree of saturation of the ammonia
vapors. Once you make an acceptable exposure, write the exposure time
down on paper and keep it near. Refer to it for the basis of all other
exposures in that series of foils. When running multiple overlays for
registration on a master viewgraph, run all foils for that viewgraph in the
same direction to minimize the distortion caused by shrinkage or expansion
from exposure to the heat of the light source.
To expose and develop a diazo foil, use this table:
Remove a foil from its light-proof package.
Locate the manufacturer's nick and place it in the upper-left corner
as you face the foil. This ensures that the emulsion side is up.
Place the master artwork either face up or face down on the foil.
Emulsion to emulsion between art and foil results in images with
the least distortion.
Feed combined art and foil into the machine for exposure.
Exposure is variable. Once you obtain the correct exposure, write
it down and use it as a basis for all other exposures.
The art and foil will exit the exposure section of the diazo machine
and the machine will automatically separate the art into the forward
bin while the diazo foil continues into the development section.
Develop the foil only long enough to obtain maximum color
saturation. In some cases, you may have to slow down the speed of
The developed foil exits the machine either to the top bin or the bin
in the back of the machine.
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