Novel Experimental Approaches for Making Pigment Prints

Writer and photography / Paul A Lehman, MSc.

It is well recognized that the Carbon Print is considered by most as the quintessential historic pigment process. However, the process of making a carbon print is challenging and requires skill and patience. I struggled through this process in the late 1990s, with some moderate success. At that time, I began to explore alternative methods in the hope of finding a simpler, faster pigment print process, yet one that would retain the grayscale range of carbon, and still demonstrate the image surface texture unique to carbon prints.

An ideal alternative pigment process would:

1. Negate the need for pre-made or commercial carbon pigment tissue.
2. Negate the need to transfer the intermediate image to the correct perspective.
3. Provide the ability to prepare emulsions and print within an hour, or less, per print for rapid process adjustments and refinements.
4. Retain the ability to use powder or liquid pigments of any color.
5. Utilize readily available (and conventional) chemicals.

Through initial exploration, three processes were developed. However, these are to be considered experimental, as all variables and limitations have yet to be evaluated or optimized (e.g., best negative density and range, optimum chemistry ratios, the influence of paper and pigments used for the final print, etc.). Nonetheless, the basic process for each is provided in this manuscript, including initial values for each process to use as a starting point. At this point, nothing is cast in stone.

I’ve named the three methods:

1. CarboGel process
2. Carbon-Q process
3. Burnt Plate Oil process

To give context to these methods, I developed a classification system to the historic pigment processes. In the simplified diagram below, the most common pigment processes are categorized first by base (gelatin vs. gum arabic) and then by image transparency (negative or positive). The 3 experimental methods (blue text) fit into the hierarchy of the other processes ,as shown. It would be interesting if someone were to investigate if these new processes would also work with a gum arabic base rather than gelatin. The first two, CarboGel and Carbon-Q, have been previously described, with detailed discussion on the methods, in The World Journal of Post-Factory Photography (Issue #9, April 2004). I recommend reading this issue if it is still available. (Check out: AlternativePhotography.com/post-factory-photography/. where Issue 1 is downloadable for free and details for ordering issue #9 is available.) However, there is sufficient information provided here to begin exploratory evaluations into these methods.

Substrates suitable for the pigment processes

I used digital negatives/positives made with a generic curve or actual original negatives. Further work needs to be performed to optimize the density curve for each. The digital substrate I used was Pictorico® inkjet film. Final paper supports were those artistic papers popular for alternative processes.

Method #1: CarboGel Process

The CarboGel process is gelatin based without the need for pre-made pigment tissue. The recipe below is for a 50 mL volume of emulsion, sufficient for multiple prints. Ammonium dichromate was used as the sensitizer. The Mylar® sheet, a transparent plastic film (or an equivalent clear polyester film), is available at most craft stores and mail-order suppliers. The Mylar® film, in contact with the negative, should be the thinnest Mylar® available (e.g. 7 millimetres or thinner) to keep the print image sharp. The isopropyl alcohol (“rubbing alcohol”) is optional but aids as a surfactant in the removal of small air bubbles and surface foam in the gelatin emulsion during preparation. This alcohol, on a lint-free cloth, can also be used to clean the Mylar® film and glass plates of dust and oils if necessary.

Emulsion for 50 mL (w/v):

• 10-14 g Gelatin (10 – 28%)
• 2-6 g (or mLs) Gouache watercolour paint (or suitable alternatives)
• 0.5-1.5 g Dichromate (1-3%)
• 5 mL Isopropyl alcohol (optional)

Gently heat the gelatin first in water until dissolved, and then add the other ingredients.

The CarboGel Pigment print Process

1. Pour and spread a thin layer of emulsion onto a Mylar® sheet, a bit larger than needed to accommodate the size of the negative. Once set (but not dry), overlay the emulsion with a second Mylar® sheet. As bubbles or gaps may occur under the second sheet, invert the sandwich to have the original sheet face up.

2. Apply the negative onto the surface of the Mylar®. Overlay with a glass sheet to ensure flat contact. Expose to UV light. I use BL fluorescent bulbs at about 8 inches. Exposure may take 10-20 minutes. Remove the negative, and transfer the exposed gel and Mylar® sandwich to warm water (110-120°F) to develop.

3. Replace the hot water as necessary until all excess pigment has been removed and the two layers of Mylar® have separated. The image can be seen on the original Mylar® sheet.

4. Transfer the Mylar® sheet that retains the image onto a final support (cool water-dampened artistic paper). Gently squeegee or roll with a brayer to ensure full contact. Hang to dry. As the paper and image dry, the Mylar® sheet will dislodge from the image without any assistance.

Method #2: Carbon-Q Process

The Carbon-Q Process is a simplified variation of the Ozotype. A transparent positive is used rather than a negative. The chemistry is prepared in two parts, a dichromated paper (sensitized final support), and a “tissue” which provides the source of the pigment. The overall process takes advantage of the chemical reaction of hydroquinone with unexposed dichromate to harden the pigment-rich gelatin.

Emulsion for 50 mL (w/v):

• 0.5-1.5 g Dichromate (1-3%)

Dissolve in water and apply to final paper support by floating or brushing on. Allow it to dry.

Tissue for 50 mL (w/v):

• 5-10 g Gelatin (10-20%)
• 1-3 g (or mLs) Gouache watercolour paint (or suitable alternatives)
• 0.05-0.25 g Hydroquinone (0.1-0.5%)
• 5 mL Isopropyl alcohol (optional)

Gently heat the gelatin in water first until dissolved, and then add the other ingredients.
Once applied to the paper support as a thin layer, allow to solidify but not to dry.

The Carbon-Q Pigment print Process

Sensitize your final paper support with the dichromate solution and allow it to dry. Place the transparent positive onto the paper and secure it in place with a sheet of glass to ensure flat contact. Expose to UV light as previously described. Meanwhile, prepare the pigment support on paper or Mylar®.

1. Sensitize your final paper support with the dichromate solution and allow it to dry. Place the transparent positive onto the paper and secure it in place with a sheet of glass to ensure flat contact. Expose to UV light as previously described. Meanwhile, prepare the pigment support on paper or Mylar®.

2. Sandwich the exposed dichromated paper (a faint image should be visible, and with practice, could be used as an exposure guide) face down onto the pigmented gelatin layer on the support paper. Overlay with a glass sheet with a weight, to ensure flat and complete firm contact. Maintain the sandwich for 5-10 minutes, or longer, if necessary. Do not allow it to dry.

3. Transfer the sandwich for development in warm water as previously described. Change water as needed until all excess pigment has been cleared. Remove the final image from the water and hang it to dry.

Method #3: Burnt Plate Oil Process

This process is a variation of the Oil Print process, but has one very important feature: Burnt Plate Oil is miscible in the water allowing for water clean-up without the need for toxic petroleum-based solvents. Burnt Plate Oil, with added pigments, can be purchased through art supply dealers online, or you can purchase the base oil and add your own pigments. Consider the procedure below as a very early evaluation, as an initial exploration into the process. The example prints shown suggest that the final support paper may require additional sizing or a different paper to avoid background granular staining in the highlights or a different pigment ratio.

Emulsion (50 mL) (w/v):

• 5-10 g Gelatin (10-20%)
  Heat in water until dissolved, float or paint onto a support, and allow to dry.
  Repeat 2-3 times as needed.
• Brush sensitize the gelatin layer with 0.25-1.0% Dichromate
  Allow it to dry.
• Pigment: 50:50 (v/v) Burnt Plate Oil (containing pigment): Water

Burnt Plate Oil Pigment print Process

1. Coat the paper with gelatin and allow it to dry. Sensitize gelatin with dichromate, and allow it to dry. Place the transparent positive onto the paper and secure it in place with a sheet of glass to ensure flat contact. Expose to UV light as previously described. After exposure, place the paper in warm water (a faint image should be visible). Replace the water as necessary to clear out the un-exposed dichromate.

2. Brush on, or roll on with a brayer, onto the image, the 50:50 mixture of pigmented Burnt Plate Oil in water. Once coated, use a gentle, room temperature, water rinse to remove excess pigment. Hang to dry.

Conclusion:

Give these novel methods a try, and feel free to experiment to optimize the chemistry and process steps. Please share if improvements or suggestions are found.

Paul A. Lehman has studied the history of photography and classic print processes for over 30 years. His personal collection contains several hundred vintage prints representing over 15 historic print processes, as well as several hundred cameras and books. Paul has worked in silver-gelatin, salt, albumin, cyanotype, kallitype, Vandyke, Oil, and Carbon print processes. Paul has recently retired (12/2021) after 50 years of his professional career in pharmaceutical and laboratory research. His education includes science degrees from Baylor and Incarnate Word Universities, a Bachelor’s of Business Administration degree from Incarnate Word, and a Master’s of Science degree in Pharmaceutics from the University of Washington, Seattle.