The materials contained in this lesson were derived from
the following publications:
DA Pam 325-10 and STP 11-
responsibilities include preparing overlays for graphics and maps,
graphics for various types of direct projection, and television graphics.
This lesson presents some of the methods available to perform these
PART A - METHODS OF REPRODUCING
The Diazo Process.
This reproduction process provides you with the capability of producing
standard paper copies or viewgraph slides of original graphics. However,
this process allows only a one-to-one reproduction ratio from the master.
No reductions or enlargements are allowed.
a. Diazo Process Materials.
This process uses specially treated
film and paper and a diazo machine to develop these materials. The film,
or foils, and paper have a special coating of diazo salt and an azo
The diazo salt used to treat the foil or paper is light
sensitive, especially to ultraviolet light.
(1) Chemical change. When you expose the coated foils or paper to
an ultraviolet light, a chemical change takes place that will not allow
an image to form. By not exposing the coating to the ultraviolet light
and developing it in an alkaline medium, such as the vapors of commercial
ammonia (ammonium hydroxide), the diazo salts combine with the dye to
form a colored image, as determined by the type of dyestuff on the foil
(2) Methods to develop diazo foils.
There are two different
methods used to develop the diazo foils: dry developing and ammonia
developing (figure 2-2).
The dry method has both the diazo and the
coupler included in the sensitizing formula, stabilized by a mild acid to
prevent premature coupling. The ammonia method has the developer on the
paper and the coupler is in the developing solution.
The diazo process has three basic steps: (1) preparing the master, (2)
exposing and developing the diazo foils, and (3) mounting the foil.