Straight printing on RA4 paper is great fun and it’s what I do most of the time when I print color in the darkroom. But the RA4 process has several tricks up its sleeve. The other day I decided to revisit one of those tricks I had played with briefly some years ago: bleach and redevelop. Here’s an example of what it does and how it’s a useful took in boosting print contrast without saturation going overboard.
What’s this “bleach and redevelop” thing anyway? I’ll try to explain, simplifying matters a bit in the process. Color RA4 paper contains light sensitive silver halide (mostly silver chloride) and dye couplers. After exposing the print, the developer develops the exposed silver halide, which creates a byproduct of the developer, and this in turn combines (couples) with the dye couplers to form a visible dye: magenta, yellow or cyan.
In regular processing, the next step is a blix, which stands for bleach-fix. In this step, the developed silver is bleached, which means it’s reverted back to a silver halide. The other part of the blix, the fixer, turns the silver halide into water-soluble compounds that diffuse out of the emulsion. After washing, only the colorful dyes remain in the emulsion as the visible image.
Note that the silver in the process is sacrificial: it does not form part of the final image, and only serves to make the developer create the necessary byproduct for subsequent dye formation.
We can modify this process a bit by giving the silver another go. After developing the print, we can bleach the silver image back to a silver halide…and develop it again! What happens now, is that the developer will create some more byproducts, these will in turn form more dyes with the couplers, and the image will be intensified as a result. To prevent unexposed silver from playing along in this second development step, we fix it out after the first development step. The process thus becomes:
- Expose the print
- Develop in RA4 color developer
- Stop bath
- Fix out unexposed silver
- Bleach exposed and developed silver
- Go back to step 2: develop again.
The convenient thing about this process is that anything after step 5 can be done in daylight. Well, technically, you could even turn the lights on after step 3, but I prefer to play safe and wait until the unexposed silver has been fixed out, as it might otherwise print out and create fog.
In principle, the process can be repeated over and over again. This isn’t very useful, since at some point, there are no more dye couplers left for the developer byproducts to react with. Moreover, dyes tend to form in places where you don’t want them; especially cyan dye tends to form around dark image borders and sometimes even at random across the sheet. In my experience, the useful limit to the number of bleach & redevelop passes is two – or three developments if you include the first time the sheet is developed, right after exposure.
At the end of the process, there’s the option of either leaving the developed silver in the print, or to bleach and fix out the silver image. In my experience, it does not matter much for the end result, since the silver image is rather faint anyway. It tends to add a little density and reduce saturation a bit. I usually welcome both effects, so leave the silver image in place.
Since the bleach & redevelop process adds significant density on top of the initial image, it’s necessary to underexpose the print because it will otherwise end up too dark after the redevelopment step(s). In my experience, taking a straight print as a starting point, subtract 30% to 50% from the exposure time. It takes a bit of trial and error to get it just right. I find the exposure time is quite critical; a small difference in exposure time makes a very pronounced difference in overall print density. This is because the bleach & redevelop process essentially amplifies the initial image, and as such, it boosts contrast a lot but also emphasizes small differences in exposure.
The straight print shown above was exposed for 3 seconds. For the following bleach & redevelop print, I exposed the print for only 1.6 seconds. I also made versions exposed for 2.0 and 1.4 seconds, but the former was decidedly too dark and the latter a bit too light. The print below was bleached and redeveloped twice, and the print was not bleached or fixed afterwards, so the silver image is part of the final print.
Note how in the print above, the overall density in the light areas is similar to that in the original print, but the shadows have significantly increased density.
There is also a distinct cyan shift, which is mostly due to accidental cyan dye formation. If desired, this can be compensated for by adjusting the filter settings in exposure, but I didn’t bother for it in this example. Note also how the black print border has some cyan ‘halation’ around it, which tends to become worse as the bleach & redevelop process is repeated. The print above was bleached and redeveloped twice. Doing it only once makes the cyan shift far less apparent.
In terms of chemistry, this process calls for a bleach and a fixer that aren’t normally part of the RA4 process. Fortunately, black and white chemistry works great here. For the fixer, I generally use whatever fixer I have on hand. For the print above, this happened to be a C41 film fixer that I often use for anything, but any old fixer will do. For the bleach, I mixed half a teaspoon or so of potassium ferricyanide and an equal amount of potassium bromide in 700cc or so of water. The quantities aren’t critical. According to The Naked Photographer in this video, using a C41 bleach instead of a ferricyanide/bromide bleach prevents the cyan staining issue discussed above altogether.
For the bleach and fix steps, I stuck to the same 90 seconds I used for development, which offers a built-in safety margin – and it saved me the trouble of having dial the timer to a different time…
One final note: the wash steps are absolutely crucial! These are the problems you can get if you try to get away with just a brief rinse instead of a wash of a couple of minutes and a few changes of water:
- Insufficient wash between fix and bleach: carryover fixer in the emulsion will form Farmer’s reducer together with the bleach, removing the silver image. Essentially this makes a (short-lived) blix, and the redevelopment step won’t work afterwards, or will produce very uneven results.
- Insufficient wash between bleach and redevelopment: this tends to emphasize excess cyan dye formation, creating cyan stains and/or fog all over the print. Using a C41 bleach instead of a ferricyanide bleach should help or even entirely prevent this issue.
Well, the story is actually long in comparison with the fairly simple process it really is. Give it a try sometime; you’ll find it’s actually pretty straightforward. The underlying chemical processes are complex, but as a printer, we fortunately don’t always have to be bothered with the gritty detail!