Re: Van Dyck and Kallitype
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 Arches Platine).
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?
-- Jordan Wosnick firstname.lastname@example.org