> Klaus
Ammonia "slows" the tissue as a result of its raising the pH of the
dichromate sensitizer. Furthermore, the addition of ammonia to
dichromate also changes its color from a deep reddish-orange to a light
lemon yellow. This change in color reduces the light filtering effect
of the sensitizer, allowing the exposing light to penetrate more deeply
into the pigment film, resulting in an increase in "contrast".
Charles