Re: Vandyke Variables

Richard Sullivan (richsul@earthlink.net)
Tue, 16 Jun 1998 10:04:59 -0600

Sam Wang says:
>> The biggest problem that no one else seems to have noticed, however, is the
>> way the solution ages, along with the precipitation of the silver in the
>> solution, affects the image. After intitial testings, I've found these
>> differences between freshly mixed Vandyke solution and ones several day
old:
My guess is that the differences are caused by the silver precipitating out
>> of the solution. Less silver, less dark.

Judy's comments about the ferric ammonium citrate being ill defined are on
target. What this means is that every batch is different -- well I've been
told by manufacturing chemists that it is "better." I do think the current
stuff is better, but it needs more tartaric acid than traditional formulas
call for. Extra doesn't seem to hurt so you can increase the amount of
tartaric acid by about 20% and the silver precipitating out and all of that
will go away.

We'd mix up a few liters for sale and pack in 100 ml bottles and a day or
so later they'd all have silver precipitate in the bottoms. Quite a
nuisance, and even more so if you have shipped some to a customer. Like we
sell it by the liter sometimes to schools. If you get the preciptiate, just
keep slowly adding tartaric acid until it is all dissolved.

You will also find that it prints better as well.

--Dick Sullivan

Bostick & Sullivan
PO Box 16639, Santa Fe
NM 87506
505-474-0890 FAX 505-474-2857
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