DIY ILFOCHROME CHEMISTRY
by Terry Dennett, Institute of Zoology, London
The Club has successfully pioneered and kept the flag flying for colour film home processing so it is perhaps useful now that the E6 process has been standardised to think about doing group work on the llfochrome colour reversal print process which is very much a complimentary partner to our beloved slide reversal film. What follows are a few notes of my own work with Ilfochrome paper to try to start this project off...
The Ilfochrome Dye Bleach process has been greatly improved over the years and is still the most stable of all the generally available colour processes - in fact the colour microfilm used by libraries and government archives is based on a version of this process. This was, I am told, the only thing that came up to specification for long term storage - much to the disgust of the rest of the industry. Currently Ilford have been claiming a 200 year life for correctly processed and stored prints.
My first contact with the Dye Bleach process was in the I 960s when, as a young photographic technician, I went to an early trade demonstration of Cibachrome, as it was then called. The demonstrator came in kitted out in rubber apron, gloves and a face mask - the bleach then was essentially sulphuric acid. The plastic base of the paper was so sharp at the edges that you could cut yourself if you weren’t careful. And the contrast was so high that most serious users resorted to making unsharp masks to keep highlight and shadow detail. A little later an expensive glass Auto masking system was developed for Pro lab use. Things have moved on since then, and the basic chemistry is now much more environmentally friendly. The processing has been reduced to three simple baths and a couple of wash stages which makes it ideal for the home processor who can afford the convenience of a Jobo or similar drum processor.
Alternative ChemistryA number of people have looked at the chemistry and patents and proposed DIY dye bleach solutions - both to match the qualities of the commercial chemistry and also to produce results not possible with the commercial product. Much of this early work was aimed at taming the contrast problem by modifying the developer, but one company in the USA offered an interesting alternative two stage Bleach consisting of separate silver and dye bleaches, which may be worth taking up again. I see from the Internet that the company still exists, but sadly no longer lists any Cibachrome chemistry.
Two bath developers were successfully used with the earlier high contrast materials and the techniques were fully described by Hal Berg (3), but these no longer work because of fundamental changes made in the structure of the material, which now includes integral contrast reducing masking layers.
Today’s chemistry now uses a silver solvent in the developer to complete the masking layer process. Ordinary development without solvent as in the two-bath system will not generate these masks and only produces indifferent prints.
Alternative Chemistry for Today’s Materials
This knowledge was my departure for formulating a new series of developers through which I could vary both the colour balance and contrast scale, simply by changing the proportion of the silver solvent in the developer. As noted above, without silver solvent in the developer we only get poor prints, often with a colour cast that won’t filter out. Adding progressive amounts of silver solvent to the developer reduces both the cast and optimises the print contrast.