"Lew" wrote in message
t...
When the hydroquinone only formula I posted earlier in
this thread made no discernable difference in my neutral
toned paper, I added more carbonate to shorten the
developing times & now I can't tell the difference between
it and Dektol. (Begging the question: what does metol do?)
-LS

"Richard Knoppow" wrote in
message
ink.net...

Snipping...
Metol is a very efficient electron transfer agent.
Hydroquinone by itself is a very low activity developer.
When used at quite high pH it is suitable for very high
contrast developers but cab be a fine grain (and brown tone)
developer at lower pH provide one is willing to deal with
the great emulsion speed loss caused by its inefficiency.
In most Metol-Hydroquinone formulas the Metol is the
primary developing agent. The two agents in combination are
super-additive over a range of pH, meaning the resulting
densities are greater than either agent would produce by
itself. The combination also has a mutual regenerating
effect. At low pH, as in D-76, the regenerating effect
exists but the super additive effect does not. D-76 is
nearly as effective with the Hydroquinone left out.
Metol, OTOH, works well by itself and is an effective
developer even at neutral pH (as in D-25).


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Richard Knoppow
Los Angeles, CA, USA