>>The only developing agent that will last even an hour without an inhibitor
>>like sulfite is Amidol, and that's not particularly good for films
>
>When we conducted a series of tests some years ago to discover the best
>combination of film and developer for platinum printing there was no doubt that
>amidol came out streets ahead of anything except PQ Universal for tonal range,
>separation of tones and gradation.
You are absolutely right. I wrote my piece without thinking too hard. Amidol
is noted for not requiring an alkali - still needs sulfite. In fact, in low
sulfite concentrations it has an extremely short life, as do most developing
agents. It is a fantastic developer for prints as it enables a broad tonal
quality with rich grays and blacks. For film, it is, as you say, very soft
and was never used much. (In these days, I can't imagine anyone using it for
anything because of the outrageously high prices being asked for it.)
>On the other point of amidol working without sulphite I thought that the huge
>amounts of sulphite in the standard recipes kept the thing going.
Amidol requires sulfite to react; it doesn't require alkali, which makes it
different from most other compounds used for developing. In fact, it can be
used in an acidic solution, in which case it does not oxidize (Br: oxidise)
rapidly, but it also works very slowly.
>Have I again been believing too much of what I have read in books ?
No, you caught me with my knowledge unconnected to my brain. Though some
people don't believe it, I am human.
Incidently, I used to use Amidol developer with Dassonville Charcoal paper
and the results were absolutely delicious. Both are now quite obsolete.
Thanks for bringing me back to reality.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net