Black
and white negative developing in its most
simple form consists essentially of two
chemicals, developer and fixer. When exposed
stock is immersed and agitated in developer
(in a darkroom), the grains struck by
light are dyed opaque. The unexposed grains
dye at a much slower rate. Soon, an image
begins to form. Left too long, the entire
film would become dyed so the developing
time is critical. Even removed from the
developer, the film is still being dyed
- any new light (if the lights are turned
on) would turn the entire film black.
To arrest this dyeing process and make
the images on the film permanent, it is
immersed into a chemical called fixer.
Fixer neutralizes the developer chemical
and dissolves away the undyed (unexposed)
grains, leaving only the grains that were
dyed black. Once all of the unexposed
emulsion has cleared the film, the image
becomes fixed permanently to the base
and no longer sensitive to light. The
lights can now go on and the film dried.
Color negative has multiple layers of
emulsion (cyan, magenta, yellow, anti-halation,
etc.) and requires extra processing steps
but is essentially the same chemical process.
I've developed color negative with black
& white chemicals using nothing but
a coffee mug and a wristwatch for an exposure
test; sure, the color was an absolute
horror but the density of my exposed negative
(which was the information I wanted) was
determined on the spot.
