Re: Van Dyck and Kallitype
Maybe Sandy can chime in here about the double coating, and I may be drawing an erroneous comparison, but sometimes with PT/PD double coating improves the smoothness of the print and DMax because the first coat neutralizes the paper and thus the second coat is laid down on a slightly acidic paper. Have you tried presoaking the paper in Oxalic Acid, or Sandy, would you not recommend this?
Precision Digital Negatives - The System
PDNPrint Forum at Yahoo Groups
In a message dated 9/25/06 10:07:41 AM, firstname.lastname@example.org writes:
I'm a bit late to this party, and I may be hijacking the thread a
little, but I find it interesting that Kallitype doesn't need to be
double-coated. I like the results I'm getting with Van Dyke, but the
double-coating is killing me, as it seems to lead to blotchiness on
the prints (I've been using Stonehenge Rising, Fabriano Artistico and
I'm toying with the idea of trying Kallitypes. It's my understanding
that if I have what I need for VDB, all I really need for Kallitype is
iron(III) oxalate. But I'm a little edgy about the cost and risk
associated with buying the commerical material.
There is an experimental technique in chemistry called potassium
ferrioxalate actinometry, which allows one to make an absolute
measurement of light (number of photons per cm3 per second). It
basically uses the "Kallitype/Pt-Pd" reaction, but instead of reducing
Ag(I) or Pd(II) or Pt(II) at the end, the ferrous iron is allowed to
form a coloured complex. The actinometry mixture is made by combining
a carefully titrated solution of iron(III) sulfate with a six-fold
molar excess of potassium oxalate solution. In theory, this could also
be used to avoid the need for ferric oxalate (ferric sulfate is
cheap). I wonder if anyone's ever tried it?