From: Kerik (Kerik@kerik.com)
Date: 04/09/03-12:09:12 PM Z
Christina,
HP in the developer will increase contrast somewhat, as others have stated.
However, I really don't recommend this approach. The HP is quite unstable
and the developer contrast character will likely change during the course
of a single printing session. Enough to drive you nuts and waste time and
materials.
Sodium dichromate is more commonly used as a developer additive rather than
potassium, although I would think potassium would provide similar effects
if you balance the quantity of the dichromate relative to sodium. I say
this because this approach has been standardized (by Phil Davis, I believe)
based on a drop count of 50% sodium dichromate solution per a given volume
of potassium oxalate. If you were to use potassium, I believe you would
have to use more of it since it will only exist in solution at a
concentration of about 11%.
And finally, if you haven't already, I really recommend experimenting with
B&S's "Na2" contrast agent which is added to the sensitizer rather than the
developer. It gives you a much wider range of contrast adjustment than
available with the dichromate approach, and it doesn't cause the
degredation of print quality associated with the "Ferric Oxalate No. 2"
approach that causes so many people problems when the are starting with
this process.
Kerik www.Kerik.com
> Good morning!
> Does anyone use either hydrogen peroxide or potassium dichromate added
> to the developer or hp added to the sensitizer (the latter not for
> palladium)?
> Correct me if I am wrong here: added to the developer, dichromate will
> increase contrast? And hp will decrease contrast? Why does this happen?
> Chris
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