Many argue, as I do, that Van Dyke is one version of the processes that
depend upon the use of iron salts to reduce silver that are,as a group,
known as kallitypes.
The advantage of the Van Dyke or brown print where ferric ammomium citrate
is the iron salt, is that it is cheap and simple and quick. The prints have
the long density range of print out processes and can vary in tone, when
done properly from deep rich browns to blacks.
The version based upon ferric oxalate gives prints that are often
difficult to distinguish from platinum. There are very complicated methods
that people have arrived at to make this kind of kallitype but essentially
it is also very easy. If you substitute 12 % silver nitrate for the
platinum in the standard platinum method you will get a print that rivals
platinum. When we were all thinking up funny names for things, I climbed on
and called this version an 'agferox' print !. Remember though that when you
are using processes that use both iron and silver salts that the silver has
to be fixed and the iron has to be cleared. Only use 2% fixer (hypo) for a
short time, say 2 mins, but ensure that you wash well.
Terry King