Preparations for Alternative Printing

All the iron-based processes, and some of the others too, have working methods in common; so to avoid repetition, the equipment, materials, and handling procedures are summarized here.

The Working Environment

A benefit of the low sensitivity of alternative printing processes is that you do not need a darkroom or safelighting to carry them out. Ordinary curtains or blinds should subdue daylight sufficiently, but preferably you should work under a normal incandescent (tungsten) light: a 100W bulb, distant 2 metres or more, is quite safe. Avoid fluorescent light if you can; some types of tube have a significant UV output.
You will need a clean, flat, dry surface for preparing the sensitized paper and enough wet-processing space for four photographic dishes of an appropriate size, together with running water for print washing and a drying facility that need be no more complicated than a 'clothesline' and pegs. The sensitizers and processing chemistry used are generally odourless and no fumes are evolved, so there is no need for special ventilation in the workplace. However, clean working methods are vital and any spilt substances must be cleaned up immediately.

Materials and Equipment

The following items of equipment will be needed:
  1. Pencil
  2. Ruler
  3. Masking tape
  4. Negative blower brush
  5. White blotting paper
  6. Sheet of plate glass (4-6 mm thick and larger than the paper)
  7. Jug to measure 1 litre
  8. Hypodermic syringes 1 cc, 2 cc and 5 cc (Disposable typewithout needles)
  9. Measuring cylinder (a 'graduate') 50 or 100 cc capacity
  10. Small mixing glass (a liqueur or 'shot' glass is ideal)
  11. Scales accurate to 0.1 g, or a chemical balance
  12. Small spatula
  13. Hygrometer (as sold for use in green-houses)
  14. Several brown bottles for sensitizer solutions (ca. 50 cc is suitable)
  15. Four photographic dishes (larger than the paper)
  16. Print tongs or rubber gloves
  17. Means of print washing
  18. Timer (a wristwatch will do)
  19. Glass spreader rods*
  20. Sheets of Artists' paper suitable for coating*
  21. Contact-printing frame*
  22. Ultra-violet light source*
  23. Suitable negatives*
*The specifications for these last five items are described in detail below.

Choice of Paper

The characteristics desired in a paper for alternative printing are:
Several mould-made fine art papers intended for watercolorists or printmakers have been found to work well, including:
Fabriano 5*
Arches Aquarelle*
Saunder's Waterford*
Van Gelder Simili Japon Nacre
Hollingsworth Kent
BFK Rives
RKB Arches
Whatman Watercolour
Strathmore 500
Arches Platine
Cranes AS 8111
Cranes Crest Parchment (* these are gelatine sized, and should be avoided for pure platinum printing)

A handmade paper which has beeen specified by the author for platinum-palladium printing is the 'Buxton' paper from Ruscombe Mill.
The greatest imponderable in 'plain paper' printing is the effect of paper-manufacturers' additives on the reactive chemicals of the sensitizer. Each commercial paper has its own idiosyncrasies, which may vary from batch to batch or be changed by the manufacturer without notice. There is no substitute for personal trial and experiment.
The two sides of a sheet of fine paper often differ distinctly, reflecting the method of manufacture: the so-called 'wire' side shows, on close examination under bright light, a very fine geometrical mesh pattern; the 'felt' side has a random texture. Paper may be coated on either side, according to your taste. The watermark should always be excluded from the coated area. Always handle paper by the edges, using both hands; never touch the picture area, either before or after coating, and do not touch the reverse either, because moisture from the fingers can diffuse through.

Glass Spreader Rods

In place of the traditional brush, the more economic coating implement is a glass rod (or, preferably, thick walled capillary tube, which is usually manufactured to higher standards of straightness) of external diameter between 6 and 12 mm, having a straight central section equal in length to the width of the coating area. The end portions of the rod should be bent at an angle, using a powerful gas burner; a 'bicycle handlebar' shape: \_____/ is simple and ergonomically effective. The centre portion acts as the spreader, and determines the width of the coated area; the limbs serve as handles. This implement must be kept scrupulously clean.

Rod-Coating Paper with Sensitizer Solution

Follow this procedure:
  1. Cut or tear your sheet of paper to a size that allows generous borders around the picture area - this not only looks well, but the margins also facilitate handling and protect the image. Mark the sheet of paper very lightly in pencil to indicate the corners of the area to be coated. Time and trouble may be saved by devising a card template to guide this marking up. The coating dimensions should be 1 to 2 cm larger than the negative to allow for irregularities and make positioning easy. Avoid including any watermark within the picture area.
  2. Tape or clip the sheet lightly to a very flat level surface: a heavy glass plate is ideal. Check with a spirit level that the paper is horizontal; this is critical, so adjust it if necessary. Dust off the surface with a blower brush.
  3. Draw up the mixed sensitizer into a syringe of appropriate size, and adjust it to the required volume. (Ignore the air bubble in the syringe and take the volume reading from the bottom of the plunger.)
  4. Expel the liquid slowly and gently from the syringe (use two hands) as you move it steadily from left to right across the width of the coating area between the pencil marks at the top of the paper. For steadiness, touch the paper lightly with the syringe nozzle and try to expel an unbroken strip of sensitizer, but do not be too slow or fussy - irregularities will even out in the coating.
  5. Holding the spreading rod with one end in each hand, place the straight central portion onto the paper parallel to, and a little above, the strip of sensitizer. Then, with slight pressure draw the spreading rod down into the strip of solution. Pause briefly (a couple of seconds) while the liquid distributes itself uniformly along the length of the rod, then steadily draw the strip of solution down the paper, like a tiny tidal wave running in front of the rod. The rod is not rotated, and very little pressure need be applied. When you reach the pencil marks at the bottom of the coated area, hop the rod over the strip of solution and push it back to the top of the coating; then hop over the sensitizer strip once more and draw it down to repeat the spreading. Just five passes over the paper will suffice for its surface layer to become saturated with a uniform coating of sensitizer. The first two passes should be made quite rapidly (3 or 4 seconds each) to ensure complete wetting of the surface, and the last three as slowly as possible (10 to 15 seconds each) to allow maximum absorption. At the end of the fifth pass, drag the spreader well below the picture area, with its excess sensitizer (when you have fine-tuned the exact volume to use with your chosen paper, there should be very little waste).
  6. Gently lift off the spreader, and soak up any residual liquid left at the bottom of the coating with the edge of a clean strip of blotting paper, otherwise crystals may be formed which can damage the negative. Clean the spreading rod.

Brush Coating

This is the traditional - but rather wasteful- method, for those who prefer the 'freestyle event' and are really painters manque. It can be fun with an inexpensive sensitizer like cyanotype, but is not recommended for platinum. If you use a brush, avoid those with metal ferrules. A Japanese 'Hake' brush is very suitable.

Drying Sensitized paper

Immediately after coating, the paper should be kept horizontal for a few minutes until the liquid is sufficiently absorbed for the surface to become non-reflective. The sheet may then be hung up to dry in the dark for at least an hour before use. Alternatively some heat may be used - a stream of warm air at 40 °C for 10 minutes is adequate - but it should be noted that this treatment can influence the print colour, especially in the palladiotype process, and may cause unevenness.

Contact-Printing Frames

Some form of contact-printing frame is essential for applying enough pressure to maintain the close contact between negative and paper. The simplest option is a sheet of plate glass (4 to 6 mm thick - not 2 mm picture glass) and a flat baseboard with a thin sheet of foam rubber or plastic to take up unevenness. This sandwich is held together by strong clips. Alternatively, one of the commercial contact frames for proofing negatives may be used.
However, the versions of iron-based processes I describe give a print-out - that is, a fully detailed image is formed during the exposure and subsequent processing involves little or no development, only clearing and fixing. It is therefore a great advantage to be able to inspect the progress of the printing (away from the UV source!) without destroying the registration between negative and print. This can be achieved with a hinged-back printing frame of the traditional design common in the nineteenth-century, when printing-out was the standard practice. These can still be bought and are often of high craftsmanship (and cost), but it is easy to construct one from a strong picture frame made of extruded aluminium with a deep rebate. It is important to include an impervious sheet of rubber or plastic larger than the sensitized area sandwiched between the paper and the hinged pressure back; otherwise diffusion of air or moisture through the hinged joint may cause unevenness in printing. Very large contact prints demand more sophisticated technology - the vacuum easel.
If you prefer clean edges and a white border around your image, rather than the currently fashionable overexposed worked edges, then mask the glass front of the printing frame with a window of rubylith, or other opaque adhesive film. Such masking brings two extra benefits: it avoids the generation, in the wet processing, of large quantities of redundant (non-image) metal, which may bleed into and stain the picture area. Moreover, the unexposed but coated borders will provide a check on the effectiveness of your clearing chemistry, as evidenced by the absence of any perceptible yellow stain.
Precious negatives may be protected during contact printing by interposing a very thin polyester film -such as Mylar or Melinex- between paper and negative. The negative will be particularly vulnerable if the paper is fully humidified. Such a 'sandwich' will, of course, diminish the edge sharpness (acutance) of the print, depending on the geometry of the light source: if a diffuse 'light bed' is used at a close distance, the protective film must be no thicker than 20 microns; if a small source at greater distance is used, e.g. the sun, then more robust film of thickness 50 to 100 microns can be tolerated without perceptible diffusion of the image.

Ultra-violet Light Sources

Any light source with a substantial ultra-violet content will work. However, sources like 'sun-guns' and quartz-halogen lamps also emit infra-red radiation, which has the undesirable effect of heating the paper and drying it out as the exposure proceeds. The best sources are fluorescent coated mercury-discharge tubes, emitting mostly the so-called 'long-wave ultra-violet' (UVA) around a wavelength of 365 nm. Tubes with a peak output around 410 nm are also effective, but 'cool white' fluorescent tubes are not.
There is no advantage, and much additional risk, in employing the more dangerous 'short-wave' ultraviolet mercury lamps which rapidly damage eyes and living tissue (UVB below 320 nm, at which point ordinary glass begins to absorb strongly, and UVC below 280 nm). Long-wave UVA lamps are manufactured in several forms for reprographic purposes as well as for domestic sun-tanning. The following UV sources are listed in ascending order of cost:
  1. The sun. Free, but uncertain and variable in many locations, the sun is effectively a point source giving high acutance, and about 4 times faster than source no. 4. There is considerable heating effect however. The north summer sky is a diffuse source with about half the speed of no. 4.
  2. Small domestic sunlamps such as the Pifco 300 watt UV lamp No. 1012. These should be used at a distance of about 30 to 50 cm from the printing frame, providing about half the speed of no. 4.
  3. Mercury discharge reprographic lamps, such as the Phillips HPR 125W, used at a distance of about 30 cm from the frame.
  4. A convenient unit such as is marketed by Gordon Audio-Visual as a Diazo printer. This provides a 'light bed' of four Phillips fluorescent tubes, type TLADK 30W/05 UV, about 8 cm from the print, and is adequate for an image size up to 25x30 cm.
  5. A similar array can be made quite cheaply by purchasing a commercial luminaire fitting from a lighting supply house, which is fitted with all the sockets and control gear to take four 600 mm fluorescent tubes. UVA tubes marketed for 'insect attractors' are suitable.
  6. A domestic 'suntan bed' - if you can afford to make platinum prints this big, then the cost of lighting must be immaterial! The smaller 'facial solarium' is another convenient source.
  7. If cost is no object, a commercial mercury exposure system such as those manufactured by NuArc for the graphic arts and screen printing industry, may be obtained for £1000-£2000.
Whatever source you use, be sure to protect your eyes.

Requirements for Suitable Negatives

The light sensitivity of iron-based papers like the platinotype is about a million times less than that of silver-gelatine enlarging papers; so with the technology commonly available, they can only be contact-printed. The reproduction scale of 1:1 leaves us with three options:
Each of these strategies has something to recommend it, but whichever you adopt, it will be essential to develop your negatives to a contrast suitable for the printing process.
The density ranges required in the negativess should be the same as the logarithmic exposure ranges (logH) of the iron-based sensitizers, because there is no Callier Effect in contact printing. These vary typically from a logH of about 1.5, equivalent roughly to a 'Grade 0' silver-gelatine paper; to a logH around 2.5, which is far softer than any silver-gelatine paper. To yield a full tonal range in the print, negatives must be made with a correspondingly long density range. This will be obtained by giving a good continuous-tone camera film normal exposure, but developing it for 75% to 100% more than the 'normal' time period recommended for silver-gelatine enlargement printing.
Trial and error can be lessened by consulting the film manufacturers' published data for the variation of Contrast Index (Kodak's C.I. or Ilford's G) with development time or with developer concentration. As a guide, negatives for platinum printing should be developed to a C.I. between 0.6 and 1.0, depending on the luminance range of the subject; the softer palladium process will require negatives developed to C.I. values in the range 0.7 to 1.3, again depending on subject and interpretation. Palladium, in particular, has a long 'toe' in its characteristic curve which can confer great delicacy on the highlight tones.
These C.I. values are more or less incompatible with normal silver printing in an enlarger, so you cannot expect to use the same negative for both. A convenient compromise is to make your original negatives in the usual way for silver printing, ensuring adequate exposure giving plenty of shadow detail, and then prepare internegatives of higher contrast from them.

Making Enlarged Internegatives

For the user of 35mm and roll film formats, the original camera image is best enlarged to give an internegative, which has the added advantage that the precious original is not put at risk by the rigors of contact printing. There are several ways to achieve this:
  1. 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-339, which is available in 5"x4" and 10"x8" 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 °C with continuous agitation. This film has orthochromatic sensitivity, so a red safelight is necessary. See the Kodak literature for further information. N.B. SO-339 is a very slow material and needs a heavy exposure under the enlarger. Even modest enlargements may require a minute's exposure at full lens aperture. Remember that it is 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.
  2. 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, which are available in large sheet sizes. 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. Agfa market a continuous-tone orthochromatic sheet film, GO210p, which has the advantage that it has a variable contrast that can be adjusted by yellow or blue filters.
  3. By starting with a positive transparency from the camera (such as Agfa Dia-Direct), an enlarged internegative can be obtained in one step on the films specified in (2).If the original small-format image is a colour transparency, projection onto these orthochromatic materials (which are insensitive to red light) will not faithfully reproduce the tonal balance. To maintain this, a panchromatic sheet film, e.g. Ilford's FP4 or HP5, will be necessary, possibly with a colour head or a filter to bring the enlarger light source to a 'daylight' colour balance.
  4. 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. It is not certain that sufficient contrast for palladium printing can be achieved this way.
  5. 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. The 'Resin-coated' (RC) variety is said to work well. Variations in paper texture, including any lettering on the back, can be cancelled out by giving white light exposure to the back of the paper, in addition to the normal image exposure to the emulsion side. A test strip is necessary to determine this additional 'compensating fog' exposure.
  6. Images that have been electronically scanned and digitally stored in a computer can be obtained as large internegatives with a high-resolution half-tone dot screen by printing them onto acetate sheet. This union of ancient and modern technologies, with all its capacities for image manipulation, may provide new possibilities in the realm of negative preparation for alternative process printing.
  7. A final remark on internegatives: Lith films, if they are developed with little or no intermediate tone, are quite inappropriate to the subtle and costly medium of platinum.
©Mike Ware 1996

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