Chromoskedasic Printing Revisited

By Christina Z. Anderson Back to


A decade ago there was an intriguing article in PHOTO Techniques magazine entitled “Silver Mirror Printing and other Unusual Black and White Print Development Processes” (William Jolly, pp. 32-36, Jan/Feb 1999; also “Silver Mirror Printing Update,” p. 11, July/Aug 1999). The process looked fasci- nating. A freshly developed, but not yet fixed, black and white print is subjected to two mild photographic solutions, an activator and a stabilizer, in the darkroom and out under room light. The activator is a dilute potassium hydroxide; the stabilizer is an acetate buffered thiocyanate. Colors appear where there is white in the print: orange, brown, yellow, pink, purple, green and blue, as well as silver on normally monochrome black and white paper.

All of these colors are the result of the “Mie” effect. The first actual article explaining this effect was in Scientific American (Dominic Man-Kit Lam and Bryant W. Rossiter, “Chromoskedasic Painting,” pp. 80-85 and 136-7, Nov 1991). Lam discovered the process in 1980, but it wasn’t until 1989 that Rossiter explained how the Mie effect was responsible for the colors that appear and gave a name to the process. Rossiter’s choice of “chromoskedasic” is Greek for “color by light scattering.”

Very soon, another article appeared in View Camera magazine, by Alan Bean (“The Black and White Corner; Chromoskedasic Painting,” pp. 40-43, Sep/ Oct 1992). At the same time, Professor Jolly, a chemistry professor at the University of California, Berkeley, began extensive research into the whys and hows of “chromo.” Lam obviously inspired many.


Jolly’s first article on the “chromo” process preceded the 1999 silver mirror printing article by years (Darkroom and Creative Camera Techniques, “Chromoskedasic Duotone Pseudosolarization Using Development Fogging,” pp. 30-31, Nov/Dec 1992). His enthusiasm for the process is quite apparent, as he ended the article with this statement: “I have not worked out all the details of this method, but I feel that it is such an exciting process that I should not delay in letting the readers know about it, even in its present imperfect state.” Jolly wrote another update to the process in the same magazine in 1993 (“Chromoskedasic Pseudosolarization Update; Popular Technique Improved,” pp. 28-31, Sept/Oct 1993), and then five years later, the article on silver mirror printing.

The Mie effect states that a black and white print is normally monochromatic because the silver particles that remain in the print after fixing absorb all color and reflect black. In chromoskedasic printing, the silver particles are carefully managed with different chemicals, with or without exposure to light, to become different sizes. These different-sized silver particles scatter light in different ways to produce the different colors. Smaller particles will look yellow; larger particles will look red.

In 2000, I, too, became fascinated by the chromo process. That year I began to teach photography at Montana State University in Bozeman, Montana. In my Experimental Photography class, one full lab day was devoted to Sabatier processes based on Jolly’s techniques. In this very wild and crazy lab, 18 students learned traditional and duotone Sabatier (usually incorrectly called “solarization”) and “chromoskedasic pseudosolarization” (what a mouthful) all at once. Yells of “Flashing!” preceded short bursts of light in a normally darkened lab. Yet as much as traditional and duotone Sabatier had become predictable for me, successful chromo with appreciable plated silver remained elusive. Students had no problem achieving unusual colors of red, yellow, bronze, pink, etc., but the silvering out was intermittent at best.

Three serendipitous happenings occurred to change this unpredictability. The first was a chance meeting with Alan Bean in 2007. Many emails have gone back and forth between us, and my process outlined below rose out of Bean’s tray chromo pro- cess equally as much as Jolly’s and Lam’s processes. The second serendipitous happening came from Freestyle Photo’s Eric Joseph, Sr. V.P. of Merchandising and Product Development for Freestyle Photographic Supplies. Because I am a member of Freestyle’s Education Advisory Board, Joseph asked me if there was anything Freestyle should carry that they didn’t already. I told him of my frustration with the discontinuation of the two chemicals required in the chromo process, S2 Activator and S30 Stabilizer. It was no longer possible to teach chromo in my Experimental Photography class because of this. Over the last year of R&D, Joseph found a company willing to create the chemistry, and Freestyle is now supplying it (see freestylephoto. biz). Another company that makes similar chem- istry under a different name is Clayton (Industrial X-Ray Activator and Stabilizer).

Ghost Town

The third serendipitous happening occurred from a mistake on my part. I was still trying to achieve predictability with chromo, as well as find a way to make the process more student-friendly. Jolly’s formulas were pretty complex: 117 parts here, 123 parts there. I needed to simplify the formula to a quick and easy method. On one particular day of messing with different chromo formulas, immediate and gor- geous silvering out occurred all over the face of the print, on the very first print through the bath and every one thereafter. I was ecstatic! It was quick, easy and predictable! All my testing in the darkroom had finally paid off. Or so I thought. The following day, I went back in the darkroom again, mixed up a tray of chemistry expecting the same glorious results and…nothing. What had gone wrong?

In retracing all steps, I realized the only difference. The day before I had used a different developer in the mix—Tektol Standard (available from Freestyle and other places). I assumed from the name similarity that Tektol was generic Dektol, completely interchangeable. Not so, I found out. Consulting the MSDS sheets on Freestyle’s website (thank you, Freestyle!) I found that the ingredients in Tektol have little in common with Dektol. Could a more predictable success depend on Tektol then? I threw out the freshly made tray of Dektol-chromo, and remixed a new tray, using Tektol instead. Instant silvering out occurred. I repeated this experiment with success several more times. Being a bit more cautious, now, to assume anything, I felt that one last test remained to cinch the deal so I could share the results in print. (Please note that the name “Tektol” is changing to “Legacy Pro Ecopro BW Paper Developer.”)

I was due to teach an experimental photography workshop at Tennessee’s Carson Newman Col- lege. I wondered if there might be some factor in Montana where I live that was responsible for the success ― water? Humidity? Temperature? Surely Montana and Tennessee differed widely enough in all of these. What better way to rule out these variables than to use Carson Newman College students as my guinea pigs? We would have either great success or perhaps disappointment, and I would feel like a failure. I held my breath as I watched the first student’s print go through the chromo bath. Instant silvering out occurred in Tennessee, too!

Jolly’s explanation for silver plating is as follows: “The fogging developer contains thiocyanate, which dissolves the silver halide by complexation. The complexed silver ion then undergoes so-called ‘physical development’ on the emulsion base, much as silver is plated out on a glass surface in the traditional chemical method of making silver mirrors. The rate of silver deposition is enhanced by making the second developer highly alkaline with potassium hydroxide (“Silver Mirror Printing,” p. 35).” My recent experiments corroborate Jolly’s explanation. The more activator used (the potassium hydroxide of the equation), the more silvering out occurs, within certain limits. Small pieces of unexposed photographic paper ― perfect because they are completely white ― can be run through several mini-baths of different mixtures of the Chromo Tray 1 to observe the different rates of silvering out and different colors from silver to bronze. Why Tektol works so well and Dektol is less predictable is something for chemists to discern. If Lam could work for nine years with the process before Rossiter explained the scientifics behind it, I can, too. At the end of this article is a list of all the chemistry involved for those who would like to solve the puzzle. My guess is that it might not be just the Tektol at play here, but perhaps other factors as well, such as water temperature or paper age. Who knows? I still encourage readers to go ahead, put play back into the darkroom, and give chromo a try. Buy the few inexpensive chemicals and recommended papers necessary: Chromoskedasic Activator about $10, Stabilizer $14 and Tektol Standard (Legacy Pro Ecopro BW Paper Developer) $13.

Don’t Panic

If you are a teacher, there is one predictability aside from silvering out that I can guarantee. With this process, you will open up new avenues of discovery for your students that will make the wet darkroom come alive. It is a process that cannot be created in a computer. It is a process that requires hands-on experimentation and an attitude of willingness to accept what happens. How enjoyable it is to see excitement and adventure return to the darkroom once again!


Materials needed:
· Best: Ilford, Multigrade Warmtone (glossy is best; RC or fiber both work well) or Ultra paper
· Arista Premium B&W Chromo Activator · Arista Premium B&W Chromo Stabilizer
· Silvergrain Tektol Standard or Tektol Black (Legacy Pro Ecopro BW Paper Developer)
· Normal darkroom chemistry (developer, stop, fix, hypoclear)

Chromo Tray 1 to make 1 liter:
· 500ml warm water
· 25ml Silvergrain Tektol Standard or Tektol Black (Legacy Pro Ecopro BW Paper Developer) stock solution (can use 70-125ml)
· 250ml Arista Premium B&W Chromo Activator
· 125ml Arista Premium B&W Chromo Stabilizer

In a liter container, add 500ml water. Add 70-125ml Tektol (Legacy Pro Ecopro BW Paper Developer) stock solution (undiluted). Add 250ml Activator. Add 125ml Stabilizer. Cap and lightly shake. The solution will smell strongly of ammonia, so letting it sit a while may help. At time of use, pour this in a tray large enough to allow you to gingerly pick up a print with tongs by the edges. Better yet, use nitrile gloved hands to move the print from tray to tray. An 11×14 flat-bottomed tray is best for 8×10 prints. If doing prints larger than this, use a 16 x 20 tray. With the latter, you will need to double the amount of chemistry to allow total submersion of the print.

Chromo Tray 2:
· 900ml water · 100ml Arista Chromo BW Activator

Red Cow

In a liter container, fill with 900ml water. Add 100ml Activator. At time of use, pour enough into a tray to be able to submerge the print under a thin layer of solution.


1. Expose and develop a print for 2/3 the time in any paper developer until print looks tonally complete―darks are suitably dark and there is some detail in the highlights.

2. Drain, rinse in water, and slip face up into Chromo Tray 1. Agitate for the first 30 seconds or so and then watch for silver to plate out over the whole surface. This will take 30 seconds to several minutes. In the darkroom it will appear as a creeping, massive gray fog. Look at the print obliquely in the tray to see if it fluoresces silver. When it fluoresces, remove it and place it face up in Chromo Tray 2.

3. Bring the Chromo Tray 2 with the print out into room light for however long desired. Color shift will occur―pinks, mauves, peaches and even blues. This part of the process moves slowly. Plan time to nurse the print along while watching. If the print looks perfect after Chromo Tray 1, you have the option of not doing Tray 2, in which case stop bath, fix, wash and hypoclear the print as usual.

4. When the print looks good, bring it back into the darkroom and stop bath, fix, hypoclear, wash and dry as normal. You must not touch the surface of the print until dry or it will mar permanently! This means either separate trays to wash each print or an archival washer with individual print slots, and no squeegeeing. Dry face up. Once the print is dry, you can polish it with a soft cloth just as you do with any silver object.


Materials needed:
· Same as above
· Three separate plastic cups
· Assortment of brushes: small and larger, fat calligraphy brushes work well

Mix these three solutions in separate cups:
1. 10ml Arista Premium B&W Chromo Stabilizer in 90ml water (10% solution; can use 10-20%).
2. 20ml Arista Premium B&W Chromo Activator in 80ml water (20% solution; can use 10-20%).
3. 15ml Tektol Standard or Tektol Black (Legacy Pro Ecopro BW Paper Developer) in 75ml water (15% solution, 1.5x as concentrated as working strength Tektol Developer).

1. Expose and develop a print as above.
2. Drain developer off, rinse with water, and bring out into room light in a flat bottom tray.
3. Immediately paint a layer of the 10% stabilizer over the entire print and watch the darkening color turn to pale yellow. After a bit, paint on some 20% activator in places where you desire a dark brown shift. It will slowly shift in time, and the amount of each solution you use will determine that—for instance, more activator and less stabilizer on the print, quicker change. If it moves too quickly, paint on some more stabilizer.
4. Paint on some of the Tektol (Legacy Pro Ecopro BW Paper Developer) solution. This is when the silvering out usually occurs.
5. The rest of the process is a repetition of these three steps, with these three solutions. Pay attention to your mark, making sure your painterly strokes are contributing to the image. When the print is how you want it, rinse, stop, fix, hypoclear, wash and dry as you would with any black and white print, being careful with the tender surface. Do not squeegee or touch it harshly.

Step wedge showing colors

Most of the time, stabilizer is brushed on first after development, and then activator. Stabilizer leans toward yellow; activator leans toward orange; developer leans toward red-orange and deep red- brown. Most often, stabilizer to activator is in a 1:2 proportion with almost all formulas I found on the process.

The more concentrated the solutions, the deeper the colors; the less concentrated the solutions, the paler the color. As Jolly has found, the color obtained is related to the pH of the developer. High pH leans toward the red end of the spectrum and low pH leans toward the blue end of the spectrum. Activator increases the pH, hence redder colors. To increase pH, you can use more activator or even some sodium carbonate powder. To decrease pH, use either 28% acetic acid stop bath or 3.5% borax solution. The more developer used in the mix, the more the orange moves toward deep and rich red- brown. If color forms too slowly, raise the pH (more activator). If color forms too quickly, reduce the pH (more stabilizer). However, changing the pH will affect the color.

There can be a color shift with some of the colors when the print is fixed, as well as when the print is dried. The blues and purples dry down to silver, which will fluoresce blue and purple in oblique light. The pinky reds will dry browner. If you want to preserve these colors as close to as they are, you can use a solution of one part of 5% sodium thiocyanate with five parts of water instead of the usual fix. Agitate in this for about 20 seconds. Make sure the developer used remains fresh or you may get a layer of amorphous, black, sludgy silver on the surface of the print. This can be wiped off gently with dampened cotton balls.

Chemistry Involved

About the Author

Christina Z. Anderson
Christina Z. Anderson is an assistant professor of Photography at Montana State University, Bozeman, where she teaches alternative and experimental process photography. Her two books, The Experimental Photography Workbook, and Alternative Processes, Condensed, have sold around the world. In the works is a comprehensive book on gum bichromate. Her work has been exhibited internationally and nationally in 65 shows and 24 states. Visit her online at