Cyanotype: Ag 41

Some time back I posted about the methods that I started using for the
iron-based processes when working with Terry King around 1990, making
use of paper that had been treated only with an iron oxalate sensitiser
which could then be developed in various ways - I used it for kallitype,
satista and platinum/palladium. I suggested that something of this
nature was the basis of the various new processes that Terry has given
the names '... Rex'.

It was thus very interesting to read the latest issue of Ag+ in which
Michael Maunder takes a fresh look at the cyanotype process in
particular,by going back to the original work of Herschel. In it he
found a number of interesting points that have been largely overlooked
by later workers. Herschel had also worked with papers sensitised with
iron salts alone and with some interesting results, not least in greatly
reduced exposure times compared to traditional cyanotype recipes which
incorporated the ferricyanide in the sensitiser. Following Herschel and
developing his ideas, Maunder is able to produce cyanotypes in camera
(an example of such a negative image is in the magazine) with an
exposure of 5 mins at f2.8 of a view in some ways similar to Fox
Talbot's window, chosen by Maunder because the daylight at the time
would have virtually no UV content. In one of the more interesting
comments he also mentions that by using ferric chloride, Herschel
produced a system that was truly panchromatic, "into the infrared".

Exposures under an ordinary halogen lamp at around 10cm using a paper
coated with just ferric ammonium citrate are 30-180s. A weak solution
of ferrocyanide (not the usual ferricyanide) is then brushed on the
exposed paper to develop it. No image should be visible at this stage
(if you get any blue, just keep on brushing until it goes.) After a
couple of minutes give the paper a brief wash (2 mins for thin paper)
and hang to dry. The image should just be starting to appear and will
take a couple of hours to gain full intensity (use peroxide if you are
impatient.)

If you are interested, I'd suggest you buy the magazine for more details
- there are some useful practical tips and many more suggestions that
might be worth following up. The sensitivity of the material is such
that a powerful enlarger with metal halide illumination (not cold
cathode) may be usable. Michael uses a slide projector. There is a fine
example of one of Terry's 'Cyanotype Rex' images reproduced with the
feature and several other features of interest - notably work by Robert
Adams and a piece by critic David Lee on how 'State Art' has taken over
photography and removed the fun and interest from it in which I found a
great deal to agree with.

Ag Autumn 2005 Number 41: ISSN 1475-116X

Peter Marshall
petermarshall@cix.co.uk +44 (0)1784 456474
31 Budebury Rd, STAINES, Middx, TW18 2AZ, UK
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Received on Fri Oct 21 14:17:57 2005