Most hand-applied emulsions require such a great amount of exposure that direct enlarger projection onto them is not practical except with special air-cooled enlargers and a very high intensity light source such as mercury vapor of pulse-xenon. Thus, contact printing is the standard meant of operation. This can be viewed as opportunity rather than limitation.
Light will go through almost anything, given enough time. Ernst Leitze made excellent reproductions of drawings which were on 3-ply Bristol board; the exposure "required three days in the best sunlight in June". More recently, Robert Heineken exposed through tomato and bread slices onto printing-out paper.
Many of the early discoveries in photography centered on the need for the reproduction of drawings and natural objects. Today we are fortunate enough to have films of various sizes and types which are fast enough in exposure time to allow enlargement onto them, direct exposure in large view cameras and copy cameras, and "photogramming" of three-dimensional objects and other two-dimensional information. With these intermediary negatives made, the transmission of information by light onto slow hand-applied emulsions becomes very efficient. Furthermore, making intermediary contact transparencies allows many possibilities for altering the original information.
Ortho Film: Standard continuous tone panchromatic film is expensive in large sizes, and must be handled and processed in complete darkness because of its sensitivity to all colors of light. Therefore, its usually more practical to use "ortho film" (orthochromatic--not sensitive to red light), which is much less expensive, available in many sizes and can be processed for continuous tonality or high contrast under red safelight. Be careful though, not to fog the ortho film under too bright a safelight or too much exposure to it.
There are many types and brands of ortho film available. "Kodalith Type 3" has been known as the best, however, most generic "litho film" with a polyester base is more than adequate quality and at least 1/3 less in price. Many companies will package the film in small quantities for institutions and are very quick in shipping.
Note: Because you can recombine and reuse the orthos you make, you will want to make and handle them well: take care of them as they are expensive and time-consuming to produce. Sheet film envelopes are available in many large sizes, or groups of orthos can be interleaved with tracing paper for protection during storage. A unique or well-made ortho might be nearly as important to you as the original negative.
Continuous Tone Orthos: Most hand-applied emulsions (Blue, Van Dyke, Salted Paper, Gum, etc.) are capable of responding to nearly as fine a tonal range as traditional silver materials, although, because of the necessary long exposures, a certain degree of transparency contrast is required to hold clear printing highlights. Unless you want to drop out detail and tonality, it is advisable to retain as much tonal information as possible. The only real problem in this stems from the fact that almost all photographic materials need a negative transparency to produce a positive image. If, as in most cases, you want a final positive image there are several ways of going about producing the negative for contact printing.
Each method varies somewhat in the complexity of the operation and the degree of tonal information it yields:
1) Enlargement of original negative to full-size ortho positive, contact printing of full-size positive to make full-size negative: This is expensive because you are using full-size film for both generations, and there also tends to be a fairly significant closing up of detail by the time you get to the contact negative stage. However, the full-size positive is often useful for printing variations, making bas-reliefs, and for printing negative color information in processes like gum printing. Another possibility is that the full-size positive transparency can be used itself as image material: used as an over-lay, painted from the backside, hung and lighted in space to create " shadow-grams ", etc.
Exposure: Choose your original negative, keeping in mind that any lack of detail in the original will be amplified in the following generations of orthos. Test strip onto ortho (making sure that the emulsion side is up--the emulsion side is usually slightly sticky and dull), process, and inspect. When enlarging try to maintain the most even tonal range as possible with good detail retention in all areas. This will prevent too great a loss of detail when contacting to the negative stage. You will not want to test strip often because of the expense, so learn to judge your negatives.
When you have determined the best exposure, make the full exposure for the positive ortho. Treat ortho film essentially as you would normal printing paper, and do all dodging, burning, and other manipulations as well. All errors will be amplified in future generational processing. Process the positive as indicated below; it is usually easier to make a number of positives in one work period, and then make the negatives in another sitting.
However if necessary, you may interrupt the washing of a positive after a minute or two (and complete it later of course), force-dry it with a hair dryer, and make the contact printing to the negative stage.
Contacting from the positive to the full-size negative should be done so that the emulsion sides of both pieces of film are in contact; this gives the sharpest information transference. Make sure that the glass you use to hold down the film is clean and heavy enough to cause tight, flat contact. It is also a good idea to do the contacting against a safe colored (red, orange, black, etc.) and/or non-reflective surface, so that the film isn't fogged by light reflecting back through the base. For the most control, contact expose with a light source such as enlarger light through a small lens aperture; this allow for best detail retention. Remember also that dodging and burning can also be done during contact printing if necessary.
Processing: Be careful not to scratch soft ortho emulsion during processing. Therefore, carry out all processing emulsion side up. The corners of sheet film tend to be very sharp, and so be very careful when processing or washing more than one piece at a time. Although small spotting can be done with Kodak opaque, it is difficult to do much about large scratches.
Tray develop with constant agitation for 5 minutes in Dektol diluted 1/8 to 1/10.
Rinse or Stop normally.
Fix as with paper depending on the strength of the fixer.
Hypo clear.
Tray wash with frequent agitation for 5-10 minutes.
Treat with Photo-Flo solution.
Hang to dry by one corner, or force-dry with hot air.
Notes:
A) Large sheets of film attract dust rather well, and care must be taken to keep the film surface clean before and during exposure.
B) The ortho density required for contact printing onto each of the various hand applied emulsions varies slightly, and you will need to go all the way through a process to find out exactly what is required. Generally though, gum printing requires orthos of slightly greater contrast, and blue and brown need flatter orthos.
2) Enlargement of original negative onto 4 x 5 Fine Grain Positive; enlargement of 4 x 5 positive onto full-size ortho: the only drawback in using 4 x 5 Fine Grain Positive, (FGP, Made by Kodak), is that you don't have a full-size positive transparency, should you ever need one. The advantages are many: the tonal capacity of FGP is much better than that of ortho film (even when developed for continuous tonality) and thus less detail is lost when enlarging from the FGP positive to the ortho negative, and it is much easier to dodge and burn during that enlargement than it is during contact printing.
Exposure: Test strip and expose from the original negative onto the
4 x 5 FGP according to the information indicated in the previous section. Again try for as extended and flat a tonal range as possible.
Processing: Fine Grain Positive should be handled as carefully as indicated for ortho processing. The only difference in processing instructions should be in the development: Tray Develop in Dektol 1/5 with constant agitation for 5 minutes. Expose and process the full-size ortho negative as outlined earlier.
3) Original B &W Positives made from Kodak's Direct Positive Developing kit, enlarged to full-size ortho negatives: This method is highly satisfactory in that it yields good quality reversal development of normal camera-exposed film, which can be enlarged directly to the negative ortho stage. Because there is only one generation, the quality loss is much less. The only drawback is that your original transparencies will be positives which are not useful in straight printing unless you like negative pictures.
In camera exposure of original film is normally metered, and reversal processing is done according to the instructions in the kit. Exposure and processing of enlarged negative ortho is according to previous instructions.
4) Another possibility is to copy your original negatives in a slide copying system such as a Repronar or camera bellows/slide attachment using negative film. This results in a roll film positive which can then be directly enlarged to the full-size negative ortho state, while still preserving the original negative for standard enlargement.
5) If you have access to a good graphic copy camera which will accept film of the size you desire to contact print from, it is relatively easy to make a silver print from your original negative and copy it (exact size, larger, or smaller) to the negative ortho stage. This method yields perhaps the best possible quality; that is why it is used professionally for reproduction. The problem is finding a copy camera that is accessible and can suit your needs size-wise.
6) Paper positive, contact printed to paper negative: A great financial savings can be made at the expense of quality (or to achieve a personal quality) by substituting printing paper for ortho film in methods #1 through 4. If you decide to make paper rather than film transparencies, be sure to use the thinnest paper possible (Kodak makes a very thin paper called Document weight and a translucent resin-coated paper available in large sizes called Trans-lite especially for this purpose); otherwise, your printing times onto hand applied emulsions will be very long. Do not use paper with the manufacturers' name stamped on the back unless you want it to appear in your print. Processing and exposure of paper negatives should be for slightly contrasty tonality to account for the density of the paper. The paper negative can be made more transparent by applying a thin coating of hot melted paraffin or a thin coat of oil to the back of the paper. One good thing about making paper negatives is that you have very good control over the tonality and image quality.
7) A final good method for making continuous tone contact transparencies is to enlarge directly from the original negative onto Kodak's Direct Duplicating Film, which exposes in reverse (that is, it is a black base film which becomes lighter the more it is exposed). This film is available in many sizes and should be processed the same as ortho film. Because there is only one generation the quality yielded is very good. The only problems are that it is difficult at first to get the hang of exposing in reverse, and the film is more expensive than most other types.