"TYING UP THE ENDS"
From Patrick Fraser (Area One)
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.