I asked my question about chelating agents for good practical reasons. I
noticed that prints cleared with EDTA tend after a time to be subject to iron
staining. I also noticed, that in my experience, that this only happened where
ferric oxalate had been used in the sensitiser. I do not get grainy prints or
lose subtle gradations in the high lights.
I am quite capable of reading books and other literature but when I do not have
a particular specialisation I find it more helpful to listen to a discussion
between the specialists and intelligent lay persons.The reading of archives
often does not answer one's own questions.
I had to deal with specialists in this way for a living for 25 years and I find
it a very effective approach as the specialists need to explain things in terms
that are accessible to the non specialist who can then communicate more
effectively with the specialist. It is often helpful as the lay person may have
knowledge that may not be available to the specialist. This is not a reflection
upon the competence or intelligence of those on either side of the discussion.
This list is a healthy forum for such discussions. This approach is as true for
engineers, physicists and chemists as it is of statisticians and photographers.
(I have severe doubts about art theorists as it would seem that they often have
nothing to say anyway.)
As to the use of EDTA as a clearing agent, which has very marked advantages over
the use of HCl which softens the fibres perceptibly, it has been suggested that
the nature of the chelating reaction is that it can and does reverse when EDTA
is used. Can this be avoided and are there other chelating agents that could be
used where this reversal would not take place ? Or is it, as Klaus seems to
suggest, just a matter of the alkalinity of the developer ?
Terry King
Terry King