Words Mike Ware
For many of the alternative processes and advanced darkroom techniques you really need to work with a big negative. But we can't all afford, or be bothered to work with, a larger format camera.
For the user of 35mm and roll-film formats, the original camera image can be enlarged to give an internegative; this has the added advantage that the precious original is not put at risk by the rigors of contact printing or darkroom treatments. There are several ways to achieve this:
Direct reversal duplicating film makes a negative directly from a negative. A convenient (but expensive) method is to make internegatives by enlarging onto Kodak Professional Direct Duplicating Film Type SO-132, which is available in 5x4in and 10x8in formats only. Dodging and burning may be carried out at this stage if desired. Very vigorous development is necessary to achieve an adequate maximum density in this material.
As a starting point for experiment, develop it in the Kodak high contrast developer D19 (undiluted) for 6 to 8 minutes at 22-24 degrees C with continuous agitation. This film has orthochromatic sensitivity, so a red safelight is necessary. See the Kodak literature for further information. SO-132 is a very slow material and needs a heavy exposure under the enlarger. Even modest enlargements may require exposures of a minute or two at full lens aperture. Remember that it's a reversal material - more exposure gives less density. Remember always to make your internegatives as mirror images: i.e. place the original negative emulsion up in the enlarger so the duplicate will make a right-reading image when exposed emulsion-to-emulsion on the print.
The longer route is via an interpositive, using normal negative-working continuous tone films such as Kodak Gravure Positive Film 4135 or Agfa Gevatone N31p or N33p. The choice of size for the interpositive will depend on your available enlarger formats and budget, but to minimise the degradation in quality introduced by the extra copying step, the larger you make the interpositive, the better. (Contact-printing an interpositive from a 35mm negative can introduce serious dust problems.) The interpositive should be printed quite heavily to ensure no loss of information; development to a Contrast Index value of one is recommended. The negative is then made by enlargement, or contact, from this interpositive, on the same film, using more vigorous development to raise the contrast. Kodak HC-110 is a convenient developer, offering control of contrast by varying concentration as well as time.
By starting with a positive transparency from the camera an enlarged internegative can be obtained in one step on sheet film. If the original small-format image is a colour transparency, projection onto orthochromatic materials (which are insensitive to red light) will not faithfully reproduce the tonal balance. To maintain this, a panchromatic sheet film will be necessary, possibly with a colour head or a filter to bring the enlarger light source to a daylight colour balance.
The sheet film on which a negative is projection-printed may be reversal-processed to give another negative directly. Kodak market a reversal-processing kit for their T-Max films.
Paper internegatives are a very economical but low-quality option. Obviously a thin-based paper stock will be needed to avoid long printing exposure times, and waxing or oiling will improve translucency.
Images that have been electronically acquired and digitally stored in a computer can be output as large internegatives onto a transparency material suited to the printer (ink-jet printers work well with Pictorico OHP film). Alternatively, but more expensively, the digital file may be taken to an imagesetter bureau for making a high resolution bromide.
This whole new area of practice is growing rapidly among alternative process workers. Consult Dan Burkholder's book Making Digital Negatives for Contact Printing for the manipulative details.
About the author
Mike Ware graduated in chemistry at the University of Oxford (1962) and obtained a doctorate by research in molecular spectroscopy (1965). He became a Chartered Chemist and a Fellow of the Royal Society of Chemistry (1982) and now studies the science, history and art of alternative photographic processes.
Mike acts as a consultant to the National Museum of Photography, Film & Television, Bradford, England, and has supervised postgraduate research in photograph conservation at the Victoria & Albert Museum and the Royal College of Art, and in alternative photographic processes at the University of Derby.
Mike conducts specialist one-to-one workshops and masterclasses in alternative printing techniques throughout the country, and has appeared on BBC Televison in the Open University series The Chemistry of Creativity (1995). Mike also has two books published by the Science Museum, London (or NMSI as it is now known) Mechanisms of Image Deterioration in Early Photographs (1994) and the more recent Cyanotype: the history, science and art of photographic printing in Prussian blue (1999) He is currently working on his third book on Chrysotype.
Contact Mike by e-mail at email@example.com