by Sandy King
History of the Carbon Process
The carbon transfer process is considered by most persons who know it to be one of the most beautiful of all photographic processes. Carbon prints are capable of a wide range of image characteristics, they can be virtually any color or tone, and the final image can be placed on a wide variety of surfaces, including glass, metal, paper, as well as various kinds of synthetic surfaces. When the final support has a smooth surface carbon prints have a highly unique quality, a discernible relief which gives them a real dimensional quality, especially prominent when the photograph is held sideways to the light. Carbon is without question the most distinctive and stable of all photographic processes, capable of presenting images with a wide range of characteristics, of virtually any color or tone, on a wide variety of surfaces. Finally, carbon transfer prints, which are made up of inert pigment(s) suspended in a hardened gelatin colloid, are the most stable of all photographic prints.
Tonal reproduction is also one of the strong ponts of carbon printing. Carbon has a long tonal scale and excellent straight-line characteristics, qualities which allows the use of fully detailed negatives with long density ranges, resulting in an even and completely linear distribution of tones from the highest lights to the deepest shadows. Compare in the following family of curves a typical carbon curve with typical silver and Pt./Pd. curves.
Figure 1. Family of Curves. Carbon, Pt./Pd. and Silver
The carbon curve has a very linear straight line curve, with little toe or shoulder, and Dmax of over 1.80; the Pt./Pd. curve has a curve with very long toe and shoulder and Dmax of just less than 1.50; and the silver curve has a short but very pronounced toe and shoulder with Dmax of over 2.0.
The carbon process as practiced today has a long history of use, having been introduced in 1864 by the Englishman Joseph W. Swan. Swan used a paper support, coated on one side with a pigmented-gelatin solution, known as carbon tissue. After sensitization and exposure this tissue was transferred to a temporary support for development. When dry the resulting pigment image was transferred to its final paper support. Swan began marketing carbon materials in 1866, offering his ready-made tissue in three colors, black, sepia and purple-brown.
Carbon was widely practiced in Europe and in the USA throughout the 19th century and well into the 20th. It was considered by many to be the aristocrat of all printing processes, and commercial carbon prints typically cost much more than those produced by any of the other process, including palladium and platinum. The market for carbon materials all but disappeared in the 1950s, although Hanfstaengl of Germany continued to produce small quantities of carbon tissue and transfer papers for monochrome and three-color work until around 1990. Ultrastable, a modern carbon color printing process based on the use of digital negatives and pin registration of the color reliefs, was introduced in the 1990s and enjoyed some popularity as a high-end color printing process, but as of several years ago materials for the process are no longer available.
As of early 2007 the only monochrome carbon tissue available in the US is that manufactured by Bostick and Sullivan in Santa Fe, New Mexico. B&S produces the tissue in several colors, including Forest Green, Nut Brown and Renaissance Black. The tissue is supplied in sheets of 36"X60" at an approximate cost of just under $4.00 per square foot. The tissue is of good quality, with a smooth and uniform coating, and is completely free of bubbles and other surface imperfections.
I strongly encourage anyone interested in experimenting with carbon printing to work first with the B&S carbon tissue before attempting to make your own. However, this article will focus on the home manufacture of carbon tissue and instructions for its use. If you use the B&S tissue be sure to follow the working directions provided by the manufacturer since they are in some ways different from the directions given here for use with home manufactured tissue.
Overview of the Process
Carbon is a contact printing process that gives a final image that comprises a pigment suspended in gelatin placed on a final support, usually paper. To make this image, a negative is placed in contact with a sensitized sheet of carbon tissue and exposed with an ultraviolet light source. This causes the gelatin to harden directly in proportion to negative densities, i.e. the tissue is hardened more in the shadows than in the highlights. After exposure the tissue is soaked briefly in cool water, then squeegeed into contact with a paper or plastic support. After about 30 minutes the tissue on its support is transferred to a tray of water at about 105°F for development. Once the pigmented gelatin has begun to melt the tissue is peeled from the support and discarded. The unhardened gelatin slowly washes away from the support leaving a relief image.
There are two major variations of the monochrome carbon transfer process: single transfer and double transfer. In single transfer the sensitized and exposed tissue is developed directly on its final support. In double transfer the sensitized and exposed tissue is first developed on a temporary support (usually a plastic of the polyester or polyvinyl family), and after drying the image is transferred to a final paper support. The final support is usually paper but may also be glass, metal, or various kinds of synthetic paper supports.
Depending on the final support one should expect some slight increase in density of a carbon print on dry-down, though it is nothing like what we expect with processes like kallitype, pt./pd. or vandyke. And, unlike a pt./pd. print, which loses much of its wet beauty when dry, carbon prints usually have a richer, more brillant look when dry than when wet.
The major steps in making a carbon print are the following.
- Make the tissue.
- Sensitize and dry the tissue.
- Mate a suitable negative with the emulsion side of the tissue and expose with a light source rich in UV.
- After exposure, separate the negative from the tissue and soak the latter in water at about 65°F for 45-50 seconds, and then squeegee the tissue into contact with the final support (single transfer) or with a temporary plastic support (double transfer). Cover the sandwich with a sheet of blotting paper, place a sheet of plate glass over the paper, and leave it undisturbed for about 20-30 minutes.
- Transfer the sandwich of tissue/support to a tray of warm water and develop the relief by washing away the insoluble gelatin. This is the final step for single transfer.
- For double transfer, allow the image on the temporary plastic support to dry and then transfer it to a final support
We will now describe each of these steps in detail. Carbon printing is a very flexible process and in every step there are multiple methods that work. However, in this article we must limit discussion to only one or two of the major variations. Consult the sources in the recommend bibliography for more detailed information on the process.
Supplies and Materials: Things You Will Need
What You Will Need
In order to make carbon prints you will need the following chemicals, materials and equipment. Most of the basic ingredients are readily available locally, and inexpensive, a fact that will be much appreciated by those used to the high cost of processes requiring precious metals such as gold, palladium and platinum.
Chemicals and Things
- Alcohol and/or Acetone
- Ammonium or potassium dichromate -- Sensitizer
- Sodium bisulfite or sodium metabisulfite – Clearing Agents
- Sugar — Plasticizer
- Glycerine (optional) — Plasticizer for arid climates.
- Thymol (optional) — Preservative
- Pigment — India or Sumi Ink, tube watercolors and numerous othe pure pigments in aqueous dispersion.
Figure 2 – Some of the essential materials needed.
- A few pieces of plate glass, 1/4" thick and two inches larger on all sides that the largest print you intend to make.
- UV light source
- Contact Printing Frame or Vacuum Frame
- Rubber squeegee
- Plastic trays about two inches larger all around than the largest print you intend to make
- Drying screens
- Access to Running Hot and Cold Water
- Scale for measuring chemicals and gelatin
- Carbon Tissue
- Final Support Paper
- Thin Mylar sheets
Stage One: Making Carbon Tissue
It is recommended that you prepare the pigmented gelatin solution, which I will call henceforth in this article the "glop," in one liter quantities. One liter gives a convenient reference point for many existing formulas and provides an adequate amount of solution to make about 10-15 tissues 8X10" in size, or the equivalent. It is not necessary to use all of the glop in one session since it can be frozen and used at a later date, weeks or even months in the future.
- Pour 900 ml of distilled water at 65-70°F into a clean wide-mouth container, either glass or plastic. While stirring, add 80 g of gelatin(Bloom 175-250), to the water and allow the solution to sit for about thirty minutes. Plain Knox gelatin from the grocery store works fine.
- Fill a small ice chest, or some other type of insulated container, with warm water at around 115-125°F. Place the gelatin solution (in its container) in the warm water and allow it to completely liquefy.
- When the gelatin solution has completely liquefied, stir in 50g of plain white sugar. The purpose of the sugar is to give pliancy to the dry tissue and prevent it from becoming too brittle. In arid climates the addition of 5-10 ml of glycerine per liter of glop can be added in addition to the sugar to prevent the tissue from drying out too much..
- Add the pigment to the gelatin solution, and stir well. Many different kinds of pigment can be used. With some exceptions almost any pigment that disperses well in water can be used. For this formula I am going to recommend either Sumi or India Ink, or a tube watercolor such as Ivory Black or Lampblack. Both Sumi and Ivory give a warm black color, while India Ink and Lampblack give a very neutral tone black. The exact amount needed depends both on the specific pigment itself and on both how much contrast you want in the tissue (the more pigment you add, the higher the contrast). For your first try, use about 15-20 g of pigment per liter of glop.
- Add water to top off the solution to 925 ml and then stir gently for a minute or so. Then add 50 ml of isopropyl alcohol to serve as a surfactant, and 1 ml of a 30% thymol in isopropyl alcohol as a preservative. Finally, top off the solution with distilled water to one liter.
- Leave the container of glop in water at about 115-125°F for at least an hour before coating. This should get rid of most of the bubbles stirred up during mixing. .
- Coat a suitable base with the glop. Although paper can be used for the tissue base I recommend a plastic such as Denril Multi-Media Vellum or Yupo, a synthetic polypropylene paper. You can coat either by pouring the warm glop directly onto an oversize base and spreading it with your fingers, or by the use of a frame of flexible magnetic sign material over a sheet of galvanized steel plate. Either way, make sure that the room temperature is at about 68-72°F for the duration of the coating.
Simplified Coating Procedure
Level a piece of plate glass, larger by several inches than the largest tissue you plan to coat.
Draw on the tissue base a rectangle with a permanent marker the size of the area you want to coat. The base itself should be at least one to two inches larger on all sides than the coating area. Wet the tissue base, squeegee it to the surface of the plate glass, and blot off with a clean towel.
For coating an area about 8X10" in size, pour about 50 ml of the warm glop into a small beaker. Gently but rapidly, pour all of the glop onto the center of the base. Then, working very quickly, spread the glop with your fingers over the 8X10" coating area.
The coating will set in 5-10 minutes. When it sets, pick up the tissue and place it on a drying screen, and set it aside to dry. Drying time will range from 3-24 hours, depending on the thickness of the coating, the temperature and humidity of the drying room, and whether or not a fan is used to accelerate drying.
Coating with Magnetic Frames
An alternative to the free hand method of coating described above is the use is of magnetic sign material over a sheet of galvanized steel. With this method you first level a sheet of galvanized steel, squeegee the tissue support to the metal, and place a frame of flexible magnetic sheeting material over the support. The warm glop is poured over the paper, and then evened out either by hand or with a rod. The magnetic sheeting material serves as a dam and keeps the coating solution confined to the area of the frame.
Magnetic sign material is available in a wide range of sizes up to approximately .060". I use the .040 thick material for most of my own work. Assuming you fill up the frame completely with glop the .040" material will give a wet coating thickness of approximately 1.0mm. Prepare the sheeting material by cutting out a frame in the material slightly larger the tissue size you wish to make. You can also use strips of magnetic tape, cutting them to form a frame of the desired size and taping the sides together with duct tape.
To coat, first place the galvanized steel plate on a flat surface and level it. Next, place the tissue base briefly in water and then squeegee it to the galvanized steel sheet. Place the magnetic mask over the paper. The magnetic material will stick to the steel through the thickness of the paper with enough force to keep the gelatin from flowing, keeping it entirely confined within the frame. Wipe off excess water with a clean towel.
Pour the pigmented gelatin on the support and rapidly spread it with your hands as evenly as possible over the area of the frame. This can be done very quickly as there is no risk of the glop running out of the coating area as sometimes happens with the free hand method of coating.
Figure 3 – Pouring the glop within the frame of flexible magnetic sheeeting.
(Image courtesy of Mike Robinson)
Figure 4 – Spreding the glop in the frame.
(Image courtesy of Mike Robinson)
It is also possible to even out the coating by rolling a steel tube or threaded rod, preheated to about 125°F, over the glop. First, pour the glop at one end of the frame and quickly spread it over about 2/3 of the surface to be coated. Then, roll the rod or tube, supported by the thickness of the magnetic sheeting material on each side, over the glop from one end of the frame to the other. This action will even out the coating over the base. The rod needs to be long enough to completely cover the cutout of the frame, and it must be rigid enough so that it does not sag in the middle. With practice one should be able to distribute the pigmented gelatin solution evenly with just one passage of the rod. The heat of the rod melts the gelatin as it passes over the glop and dissipates on contact any bubbles that may be on the surface of the pigmented gelatin solution. Done correctly, the surface of the tissue will be as smooth as glass after coating with this method. When the gelatin sets, run a sharp point such as a toothpick or sharp lead pencil around the edges of the mask, lift the tissue and transfer it to a drying screen.
Figure 5 – Spreading the glop with a heated tube.
To determine how much volume of glop is needed in to completely fill the frame and allow some excess, which is necessary with the rod, first convert all of your dimensions to centimeters, then multiply width X length X depth (thickness of the sheeting material). For example, for a tissue 11X14" in size you will need about 100ml of pigmented gelatin solution to achieve a wet coating height of .032". This assumes, of course, that the flexible magnetic sheeting being used for the frame has a thickness of .032". For sheeting of other thickness just make the above calculations to determine how much coating solution should be used for a given area. Remember, the use of a rod requires that the amount of glop you pour into the frame be slightly in excess of the calculated amount...
Preparing Final Support Papers
Single Transfer Procedure—The final support for single transfer can be either a fixed-out photographic paper or a drawing or watercolor paper that has been sized with a hardened layer of gelatin. Any good quality paper may be used, depending on the final surface desired. I recommend that beginners use fixed out photographic paper for the final support during the learning phase as the sizing of art and drawing papers is a fairly complicated procedure and can lead to much frustration in use if the sizing is not done properly.
Photographic papers are prepared by soaking in a hardening fixer for 5-10 minutes, then washing thoroughly in running water for 15-20 minutes.
Drawing and watercolor papers must be sized with a coating of hardened gelatin. Follow the directions below.
- Make up 1000ml of a 3%-5% gelatin solution, following the directions for making carbon tissue.
- Soak the drawing or watercolor paper to be sized for 5-10 minutes in warm water, then squeegee it onto a level, flat surface.
- Pour about 80-100ml of the 3%-5% gelatin solution into a beaker, add a few drops of a 40% solution of formalin to the solution, pour the solution over the paper and spread evenly using a clean foam brush.
When the gelatin sets, hang the paper to dry. For good results two or more coatings, with drying between each, is usually required.
Double Transfer Procedure—Papers used for the double transfer procedure should be coated with a relatively soft layer of gelatin that will expand considerably when wetted. This is necessary for complete transfer of the image from the temporary plastic support. If the gelatin of the paper support is too hard it will not expand sufficiently and certain parts of the image on the plastic, i.e. the highlights, will not come in contact with the gelatin of the final support, resulting in an incomplete transfer. Fixed out photographic papers are not recommended for double transfer since the gelatin of these papers will not normally swell enough to make contact with the image on the temporary plastic support, and this may lead to an incomplete transfer.
Drawing and watercolor papers for double transfer may be prepared as for single transfer with one important difference: in place of formalin or glyoxal use potassium alum as the hardener. Mix two grams of potassium alum dissolved in 100ml of warm water, then add about 5ml of this solution to every 75-100 ml of coating solution. The gelatin of papers hardened with potassium alum will swell much more than that of papers hardened with formalin or glyoxal, thus allowing complete contact with the carbon image on the temporary plastic support.
Sensitizing Carbon Tissue
Either ammonium or potassium dichromate can be used to sensitize the tissue. I use potassium dichromate for tray sensitizing and ammonium dichromate for spirit sensitizing.
The contrast of a carbon image is controlled by matching the dichromate concentration of the sensitizer to the DR (density range) of the negatives: solutions high in dichromate are used for high contrast negatives, solutions low in dichromate for low contrast negatives. Depending on the native contrast of the tissue, and the DR of the negative, the useful strength may range from as low as 1/4% to as high as 4%-6%. The strength of the sensitizer is expressed as a percent solution, an expression of weight per volume (w/v), indicating how many grams of a chemical are to be dissolved in water to make a final volume of 100ml of solution. For example, to prepare a 3% potassium dichromate sensitizer dissolve 3 grams of potassium dichromate in 90 ml of water (or 30 grams in 900 ml of water, etc.), then top off to 100 ml or 1000 ml of total solution.
Figure 6 – Tissue spirit sensitized in a 2% ammonium dichromate solution, diluted 1:2 with acetone.
Figure 7. Tissue spirit sensitized with a 4% ammonium dichromate solution, diluted 1:2 with acetone.
Figure 8. Tissue sensitized with a 6% ammonium dichromate solution, diluted 1:2 with acetone.
Carbon tissue can vary greatly in contrast so the exposure scales obtained above with the 2%, 4% and 6% sensitizers would apply only to the specific tissue used for the tests.
In actual practice carbon tissue is sensitized in one of two ways: 1) by soaking the tissue in a tray containing the sensitizer, or; 2) by brushing a solution containing dichromate and a fast drying spirit such as alcohol or acetone directly on the tissue. Tray sensitized tissue takes up to 1-2 hours to dry, while spirit sensitized tissue will dry and be ready for printing within 15-30 minutes. Both methods are capable of giving excellent and repeatable results in monochrome work when used properly. I personally prefer spirit sensitizing because the sensitized tissue dries faster than with tray sensitizing and because it is very efficient in use of materials.
As soon as the tissue is dry a phenomenon known as "dark effect" kicks into gear. Dark effect is caused by a slow insolubilization of the gelatin of sensitized, unexposed tissue. The practical consequence of the dark effect is a gradual gain in speed, accompanied by a loss of contrast. The effect is least in a cold, dry environment, and at a maximum in warm, humid conditions. For maximum consistency, maintain the working room at a constant relative humidity of around 50% and always time the exposure of the tissue to within 5-10 minutes of the end of the sensitizing stage.
Tray Sensitizing of Carbon Tissue
Carbon tissue should be sensitized under low-level tungsten illumination or with a yellow bug light. The sensitizing bath should be used at about 55-50°F. and the tissue should be left in the sensitizer for about three minutes. For consistent and repeatable work it is necessary to standardize this operation in terms of solution temperature and time of sensitizing so that the tissue always absorbs the same amount of sensitizer.
If the tissue has dried out excessively it may be necessary to first place it in a tray of cool water for a minute or so and allow it to flatten out before sensitizing. Squeegee to eliminate excess water before transferring the tissue to the sensitizing bath. If the tissue has been stored flat this step can be eliminated.
Place the tissue in the sensitizer and agitate gently for the duration of the three minute sensitizing period.
After three minutes remove the tissue from the sensitizer, allow it to drain for a few seconds, then place it emulsion side down on a clean sheet of acrylic plastic. Squeegee out the sensitizer, remove the tissue from the plastic and hand dry (or dry on a drying screen. Dry the tissue in the dark, or in a room illuminated by a yellow bug light.
The potassium dichromate sensitizer can be reused, but its printing properties change with time and it must either be periodically renewed or replenished.
Figure 9 – Pouring the dichromate sensitizer over the tissue in tray sensitizing.
(Image courtesy of Sam Wang)
Spirit sensitized tissue dries much faster than tray sensitized tissue and is also more environmentally friendly since only a very small amount of dichromate solution is needed. Ammonium dichromate is recommended for spirit sensitizing because it can be diluted with either alcohol or acetone and the stock solutions can be mixed at stronger dilutions. Potassium dichromate can also be used, but should only be diluted with acetone. To spirit sensitize a sheet of carbon tissue do the following.
Prepare a dichromate stock solution of 3X the strength necessary. For example, if you need a final strength of 2% prepare a dichromate stock solution of 6%. Then, dilute 1 part of the stock solution of dichromate with 2 parts of the spirit, either acetone or alcohol.
First, place several sheets of newspaper on a cork or foam board. Then, pin the tissue to the board to keep it from moving when brushing.
Figure 10 – Pinning down the tissue in preparation for spirit sensitizing.
(Image courtesy of Sam Wang)
Brush the sensitizer on the tissue using a foam brush. Use a one-inch wide brush for 4X5" and 5X7" tissues, a two-inch wide brush for 8X10" tissue, and a three-inch wide brush for tissue 11X14" and larger.
To coat, first wet the brush in clean water and shake out the excess. Then, pour the required amount of sensitizer directly on the tissue and brush it on: first, brush with parallel strokes on the long dimension; then repeat the process on the short dimension; and finally brush over on the diagonal.
Figure 11 – The author brushing on the spirit sensitizer in subdued light at a workshop in Toronto.
(Image courtesy of Mike Robinson)
Allow the tissue to surface dry and then brush on a second coating. To coat twice you will need approximately 8ml of total solution for an 8X10 tissue, using 4 ml for each coating. Adjust accordingly for other sizes.
After the second coating place the tissue on a drying rack or hang to dry. Drying can be accelerated by directing the air from a fan on the tissue.
Whether the tissue is sensitized in a tray oe with a spirit sensitizer it must be completely dry before it is placed in contact with a negative, otherwise the two could stick together, causing serious damage to the negative.
Negatives for Carbon Printing
Carbon printing is quite flexible and changing the strength of the dichromate sensitizer allows for the use of negatives with widely varying density ranges, from as low as log 0.9 to as high as log 2.7 and even higher. In my experience, however, the best negatives for carbon are those with a high density range which maximize the very long scale and straight-line characteristics of the carbon process. This type of negative also maximizes the relief potential of the medium when combined with the right type of tissue. The optimum negative will have a DR of about 1.8 (with a range from about .30 to 2.10) and exposure should be sufficient to get as much shadow detail as possible off the toe and into the straight line of the film's characteristic curve. As a general rule negatives for carbon printing exposed under normal lighting conditions should be developed about 1.5 times as long as would be required for silver negatives exposed under similar lighting conditions. Since increased development times also increases shadow density the EFS (effective film speed) of the film should also be increased slightly, generally about one-fourth to one-half over the manufacturer's ISO rating of the film.
Much of my present work is with digital negatives. The use of digital negatives allows one to standarize procedures and can greatly increase productivity. In making digital negatives I use Mark Nelson's Precision Digital Negative system and print on Pictorico OHP with an Epson 2200 printer. The quality of my work with digital negatives closely approximates the quality I get from in-camera negatives.
Exposing the Sensitized Tissue
Carbon tissue sensitized with dichromate has its maximum sensitivity in the UV and violet at about 350-420 nm. Its sensitivity extends through the blue but falls off very rapidly in the green to about 515nm. It has virtually no sensitivity to orange and red light. In practice carbon tissue is exposed with a source rich in UV light, such as the sun, mercury vapor or metal halide lamps, banks of BL (black-light) fluorescent tubes, and carbon arc, metal halide, pulsed xenon and continuous wave xenon plate burners made for the graphic arts. Each system has its advantages and disadvantages, but when used properly all are capable of good results. For the handy, there are a number of relatively inexpensive artificial light sources that can be put together or assembled from materials available at your local garden and home supply store. Consult the references for more information.
Sensitized carbon tissue should be exposed with a contact printing frame capable of exerting very firm pressure, or better, with a vacuum easel. The dry tissue can be very stiff and requires a lot of pressure to maintain good contact with the negative. Mask around the edges of the negative with lithographic tape to create a safe edge of about 1/4". Failure to mask the negative may result in frilling during warm-water development.
Figure 12 - Masking the negative with a safe-edge.
(Image courtesy of Sam Wang)
If the final image is to be made with the single transfer process the negative should be reversed for correct orientation of the final image. To reverse the negative, just sandwich it with its base side in contact with the emulsion. In double transfer the final orientation of the print will be correct if the emulsion of the negative is placed in contact with the emulsion of the tissue. If it is necessary to reverse the negative some loss of sharpness should be anticipated, greater with a diffuse light source such as a bank of UV tubes, least with semi-collimated and point-light sources.
Exposure times in carbon printing will vary significantly according to tissue type and light source. I expose carbon with two different light sources, a UV bank of twelve 48" BL fluorescent tubes spaced at about 4" from the printing frame, and an AmerGraph ULF-28 Continuous Wave Xenon light source. Under these conditions, typical printing times for well-exposed and developed negatives range from about three to fifteen minutes, with the major variable being the tissue itself. The AmerGraph ULF-28 prints on average slightly more than twice as fast as the bank of BL tubes.
Figure 13 – Exposing carbon tissue with the AmerGraph ULF-28 Continuous Wave Xenon light.
Transfer to Final or Temporary Support for Development
After exposure the carbon tissue must be transferred to a final or temporary support for development in warm water. The support on which the carbon image is developed must be somewhat larger than the tissue. Paper supports should be soaked for a minute or so in a tray of water at about 60-65°F before mating with the sensitized and exposed tissue. After exposure, place the carbon tissue in the tray of cool water, along with the final or temporary support, and allow it to soak for about a minute. The tissue should be brought into contact under water with the final or temporary support, then the sandwich is removed from the water and allowed to drain for a few seconds. Place the sandwich on a sheet of plate glass, tissue uppermost, and squeegee out the excess water, applying gradually increasing pressure with the squeegee. Blot off the water from around the edges, place the sandwich on a sheet of clean blotting paper, cover with a sheet of plate glass and let stand under pressure for about 20-30 minutes.
Figure 14 -Under water mate the tissue with its final support, emulsion to emulsion.
(Image courtesy of Sam Wang)
Figure 15 – Squeegeeing the exposed and wetted tissue to its final support.
(Image courtesy of Sam Wang)
Figure 16 – Place sheet of blotting paper over the tissue/final support sandwich.
(Image courtesy of Sam Wang)
Figure 17 – Placing place glass and weight over the tissue/support sandwich.
(Image courtesy of Sam Wang)
Warm Water Development of the Carbon Image
The next step is development in warm water. Transfer the tissue/support sandwich to a tray of warm water at about 110-120°F. In a minute or so the soluble gelatin will begin to melt and start to ooze out at the edges of the tissue. You should now strip the tissue from the support: starting at one corner, lift the tissue and gently pull it off the support with an upward motion. Discard the tissue.
Figure 18 – Transfer of the carbon tissue on final support to warm water for development.
(Image courtesy of Sam Wang)
Figure 19 – Strip tissue from support in warm water development.
(Image courtesy of Sam Wang)
At this point you will not see an image but a mass of melting, oozing pigment. To clear the image agitate it in the warm water with a gentle rocking and shaking motion, occasionally lifting it from the water to drain for a few seconds. After about 4 minutes most of the insoluble gelatin will have washed away and you will have a good view of the image.
Figure 20 – Most of the insoluble gelatin has washed away about 4-6 minutes.
(Image courtesy of Sam Wang)
Continue to agitate as before, lifting the print from time to time to drain. The print should be fully developed in 6-10 minutes, at which point the drain water should be clear.
There is no precise ending point to development with carbon printing so if the print is too dark after 6-10 minutes continue development in the warm water until it looks right to the eye. With extended development of 30-60 minutes it is possible to further reduce the density of the print by as much as 1/2 to one full stop.
Carbon prints have some dry down, though relatively speaking not nearly as much as Pt./Pd. Therefore, continue development until the highlights are just a bit lighter than they should appear on the final print.
After development is judged complete transfer the print to a tray of cool water (50-60°F.) and continue agitation for a minute or so, lifting it out of the water several times to drain. Leave the print in the cool water for 2-4 minutes to allow the gelatin to set, then hang it up to dry.
Veiled margins and other pigmented gelatin residue left around the borders of the print may be removed from the print by carefully rubbing these areas with a clean sponge.
Clearing the Print
Prints developed on a final paper support will have an overall yellow stain from the dichromate sensitizer. To remove this stain, soak the print in a 3% solution of sodium bisulfite or potassium metabisulfite for 5-10 minutes, or until the dichromate stain clears. Always allow the print to dry before clearing because the relief image, which is extremely delicate following development, is further softened by the clearing agents, and blistering or reticulation of the image is possible. After clearing, rinse the print in running water at 60-70°F. for 5-10 minutes. The print is now chemically stable and ready to be mounted for presentation, unless some retouching is required.
Carbon reliefs developed on plastic with the double transfer do not require clearing as the dichromate has no way of leeching into the plastic support.
Transfer of the Image from Temporary to Final Support
When printing with the double transfer procedure we must transfer the relief on its temporary plastic support to a final support. The most reliable support for the double transfer procedures is a paper support sized with a layer of relatively soft gelatin, as previously described. To make the transfer, first soak the final paper in water at about 65-70°F for 5-10 minutes. When the gelatin has swollen, which will be recognized by a soft, slimy feel to the paper, it is time to make the transfer. Now, soak the image on its plastic temporary carrier for 30-45 seconds in the same tray of water, then bring the two into contact under water. Transfer the sandwich to a flat surface, paper support uppermost and gently squeegee the back of the paper support to remove all water. Place blotting paper or a clean towel over the paper and cover it with a sheet of plate glass. After about 10-15 minutes remove the sandwich and place it on a drying rack, or hang it to dry. Depending will take several hours, or with heavy final support papers, even overnight. When dry the paper, which now carries the image, should peel easily from the plastic. In fact, it may do this on its own as it dries. If all has gone well there should have been a complete transfer of the image from the temporary plastic support to the final paper support. You should re-soak the image in cool water for 5-10 minutes to remove the gloss, then hang to dry.
The thick gelatin layer of carbon photographs can cause heavy curling and wrinkling of the print. A dry mount press can be used to flatten out the print. To flatten, warm up the dry mount press to about 180-200° F and place the print in the press between two sheets of clean board and leave for 1-2 minutes. Remove the print from the press and place it under pressure for 20-30 minutes to cool and then store it flat under light pressure. Another solution is to just place the print between two flat surfaces for a week or so, with light pressure applied with some type of weight.
If any retouching is needed I recommend the use of tube watercolors. Tube watercolors are available in a wide range of colors and unless you are using a very unusual color it should not be difficult to match the color of the tissue.
Some Common Faults and Their Remedies
Most problems in carbon printing can be traced and corrected without great difficulty. Good record keeping is a great asset in figuring out what went wrong.
Tissue is so stiff and curled that it is impossible to maintain good contact with the negative.
Cause: This results from prolonged drying of the tissue in conditions of low humidity.
Solution: Once the tissue has dried store it flat under pressure until it is time to expose.
Negative will not separate from the tissue after exposure.
Cause: The tissue was not sufficiently dry or a bit of water splashed on either the tissue or the negative before they were placed together in the printing frame. This is a very serious situation that may result in damage to the negative.
Solution: Do not use the tissue until it is completely dry, and avoid splashing water around the tissue and negative. Further, I recommend the use of a thin sheet of protective Mylar between the tissue and negative during exposure.
The image floats off or frills during warm water development.
Cause: The most likely cause is that the paper support or the tissue (or both) absorbed too much water before being squeegeed together
Solution: Reduce soaking time of the tissue and the paper support to about a minute and keep the soak water at 60-68°F or lower.
It is impossible to separate the tissue from the transfer support during warm water development.
Cause: The most common cause is gross overexposure of the tissue, which results in hardening the gelatin all the way to the base of the support.
Solution: Expose the tissue for the correct amount of time.
Most or all of the pigmented/ gelatin relief washes off the support during warm water development.
Cause: The tissue was underexposed, or perhaps received no exposure at all.
Solution: Expose the tissue for the proper amount of time.
The image frills around the edges during development.
Cause: There are several possible causes. The most likely cause is that the negative was not masked to provide an adequate safe edge. Frilling can also be caused by inadequate blotting of the tissue/support sandwich around the edges. It can also result from the tissue and support being left in contact for an inadequate amount of time and the gelatin does not dry out enough to establish good adhesive contact with the support.
Solution: Mask the negative to provide a safe edge, blot up all excess moisture from around the edges of the tissue and leave the tissue/support sandwich under pressure for more time.
The image is too dark.
Cause: The image was overexposed or the sensitizer was diluted too much.
Solution: Reduce exposure.
The image is too light.
Cause: The image was underexposed.
Solution: Expose longer.
The image is too contrasty.
Cause: The sensitizer was too weak.
Solution: Use a stronger sensitizer.
The image is too flat.
Cause: The sensitizer was too strong.
Solution: Use a more diluted sensitizer.
Small irregular blisters on the final image.
Cause: Air under pressure in the water is trapped between the tissue and the support. During warm water development the air bells expand, causing small bubbles to develop.
Solution: Prepare the transfer water well in advance to allow for the dissipation of air under pressure.
Shiny specks on the print.
Cause: Shiny specks are caused by slight irregularities in the gelatin sizing of the final support.
Solution: Apply a thinner gelatin coating, or decrease the gelatin percentage in the solution, or add a small amount of starch to the sizing solution to cut the gloss.
The final image has a yellow stain.
Cause: The yellow stain is most likely residual dichromate from the sensitizer.
Solution: Carbon prints made by the single transfer process should be cleared by soaking in a clearing bath such as sodium bisulfite or potassium metabisulfite, followed by a wash of several minutes in running water.
The final image contains streaks.
Cause: In the home manufacture of tissue one will find that certain pigments, most notably some varieties of lampblack, can cause slight streaking on the face of the tissue. This apparently results from a small residue of oil in the pigment. If this problem occurs, eliminate the guilty pigment. The problem can also result from inadequate dispersion of the pigments within the gelatin solution.
Solution: Disperse the pigment thoroughly in the gelatin solution and eliminate the pigment(s) causing the problem. Always strain the pigmented/gelatin solution before coating.
The photograhs used in this article, other than those of the author, were provided by Mike Robison and Sam Wang.
Consult the following sources for more information about carbon printing.
King, Sandy. "Making Carbon Tissue for Photogravure Printing," in Copperplate Photogravure, David Morrish, New York: Amphoto Press, 2003.
King, Sandy. The Book of Carbon and Carbro: Contemporary Procedures for Pigment Printmaking. Greenville, SC: Permanent Light Systems, 2002.
King, Sandy. "Pigment Printing with the Carbon Process, Part II," Photovision, November/December 2001, 48-52.
King, Sandy. "Carbon Printing, Part I," Photovision, September/October 2001, 42-47.
King, Sandy. "Monochrome Carbon," in Coming into Focus. San Francisco: Chronicle Press, 2000. 87-105.
King, Sandy. "Ultraviolt Light Sources for Printing with Alternative Processes," at http://unblinkingeye.com/Articles/Light/light.html
Marton, A. M. A New Treatise on The Modern Methods of Carbon Printing. Bloomington, Illinois, 1905.
Nadeau, Luis. Modern Carbon Printing. Fredericton: Atelier Luis Nadeau, 1986.
Farber, Richard. Historic Photographic Processes. New York: Allworth Press, 1998. 119-49.
Sandquist, Michael. "Carbon Printing." View Camera Nov. /Dec. 1990:4-11.
WORKSHOPS ON CARBON PRINTING
Carbon printing workshops are sponsored by Photographers' Formulary in Condon, Montana, as part of Workshops in Montana, a series of workshops on the alternative processes.
SUPPLIERS OF CHEMICALS, PAPERS AND PIGMENTS USED IN CARBON PRINTING
Art Craft Chemicals
P. O. Box 583
Schenectady, NY 12301
(chemicals and gelatin)
Bostick & Sullivan
P. O. Box 16639
Santa FE, NM 87506
(chemicals, gelatin, support papers and carbon tissue)
4150 First Avenue South
Seattle, WA 98124-5568
(support papers, Sumi ink)
P. O. Box 950
Condon, MT 59826
(chemicals, gelatin and support papers)