Although this
and earlier parts of this discussion may suggest a different conclusion
there is little doubt that the processing of Agfachrome is by far the
simplest and least troublesome of the currently available colour
processes, which includes the weighing out and compounding of the required
chemicals. At the worst a reasonably good result can be expected. 1~Tith
experience and the knowledge it brings quite excellent results can
regularly be produced. There are not too many chemicals in the processing
solutions and the time required for making up is not excessive: a working
temperature of 20 or 24 degrees Centigrade has much to commend it as it
permits an un hurried progression through the several stages. For all
these reasons it is the ideal process for those with no previous
experience of the complete home processing procedure.
However, after
Agfachrome does not appear to have been a popular one, probably because of
a limited availability of suitable formulae, some of which have failed to
make the most of the undoubted qualities of the film to the extent that it
was disclosed not long ago that the Pictorial Group of the Royal
Photographic Society.. regard it as the most acceptable for their
purposes. The only formula of which we have knowledge that is specially
suited to the Agfa process is that published annually in the British
Journal of Photography and as mentioned before is copyright and cannot be
reproduced here, but it should be available in most libraries. In fact,
however, experience over the last year has revealed that it is rather a
basic than a working formula capable of being adapted to changes that may
be made to successive emulsion characteristics. experience to date is that
only the colour developer requires.
It was just
such an emulsion change that disrupted this discussion early this year. At
the outset the aim was to adapt the formula to the use of genochrome in
the colour developer and this ‘proved to be relatively simple, but a new
emulsion numbered 3667 replaced its predecessor and was acquired in
February and appeared to be quite different in many ways to earlier
emulsions and quite some difficulty was experienced in finding a suitable
colour developer as the first indications were that the chemicals were
defective. However, this was not the case. It became evident that far more
genochrome was required than previously and whereas in the previous colour
developer only 5o8 gm/Litre as required of genochrome no less than
12.3 gm/litre was needed to produce comparable quality and density from
emulsion 3667, finally results closely resembling laboratory
processing resulted from using 8e4 gm/Litre genochrome and an
increase of the ethylene diamine content to 13.75 ml/litre instead of 8m1.
Changes of this
order are bound to cause, firstly, disbelief and later, scepticism but
they do indicate that genochrome is not a suitable development agent in
this connection although it may have been for earlier emulsions. It must
be made clear, that apart from the changes mentioned above no other
alterations were made to the formula as published.
Whilst this was
in preparation a communication was received from Frank White of Area 13
which advised that he had been using Diethyl-papaphenylene sulphate as a
developing agent with very satisfactory results, as were confirmed by the
specemin rebates and colour samples that he supplied. He used 2.8 gm/litre
in his colour developer and the formulation suggested strongly that this
quantity would be an appropriate substitution for the genochrome as
mentioned above. He indicated that when ordering a supply the formula as
below should be quoted: MW 262.33 NH2 G8H4N(
H2H5) 112304.
Finally it must
be emphasised that this discussion concerns the processing of Agfachrome
503 and L, and in particular emulsion 3667, the expiry date of which is
November 1985. The process under consideration is in substitution for the
Agfa.
process designated
“Agfachrome Process 41 It is not relevant to Agfachrome 64S, 100 or 200
all of which are understood to be compatible with process 44, which is the
Agfa equivalent of the E6 process.
Our thanks to Patrick
for his interesting and informative article and of course to Frank White
for helping him come to a satisfactory solution. This once again points to
the usefulness of the Club to exchange information with each other.
Somewhere through these pages someone will be able to help you with that
stubborn problem, so please keep your points of interest coming in.
Likewise the article on page 4 by Ted Neild will tie in with this article.