Smieglitz@aol.com
Date: 02/05/02-07:38:54 PM Z
In a message dated 02/05/2002 12:17:05, you wrote:
<<If someone knows of an effective way to control contrast with
vandyke. My tests in adding potassium dichromate to the sensitizer
before coating and/or to the developing water have all resulted in
mixed results. Are there other options?
Sandy King>>
Hi Sandy,
Are you trying to decrease or increase the contrast? It has been awhile but
I seem to recall the age of solution affects the contrast and believe this to
be a result of pH changes as silver precipitates in the bottle. I've read
somewhere that addition of more tartaric acid helps redissolve the
precipitate (but haven't actually tried to do so personally). So it might
follow that a lower contrast solution would have a higher pH...
If memory serves correctly, a freshly mixed solution (A+B+C) had lower
contrast than one aged for a week or longer. After several months the
solution started to print with lower contrast again as the precipitate
formed. However, the solution remains usable for years. Perhaps someone
else on the list has observed a similar effect?
A little overfixing or selenium toner (RST 1:100) is a way to bleach the
print slightly and decrease contrast, but unfortunately at the expense of
dmax.
To up the contrast I've usually just experimented with different papers since
I never had much luck with the dichromate either. Of course, intensifying
the negative and increased print exposure time might do the trick if this is
an option for you.
Joe
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