From: Sandy King (sanking@clemson.edu)
Date: 02/05/02-08:23:08 PM Z
Joe,
I am trying to increase contrast. The freshly mixed solution of
Vandyke sensitizer gives me a very long density range, well over
2.25, and I want to print negatives with a DR of about 1.8. They
print rather flat with no controls.
I too have speculated that the addition of ore tartaric acid might
increase the contrast of the solution but but have no idea how much I
would need to add to cause the increase?
As for the selenium toner 1:100 no way I am going to try that again.
Too many unhappy prints I have already seen from trying to make it
work.
Sandy
>
>
>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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