Print Bleaching
There are two schools of darkroom thought: some say silver gelatine print is not finished until it’s been toned; others say it’s not done properly if it’s not been bleached before the toning. I fall into the latter category.
Bleaching is a simple darkroom technique that dramatically improves most prints, as it’s the only way that makes it possible for the print to reach pure white tones. Yet bleaching is not much talked about, I suspect principally because Adams was not fond of it, plus the technique he described in The Print is suboptimal and likely discouraged many who tried it. But the reality is that every print suffers from a degree of fogging (not least because no emulsion is entirely insensitive to red light), so instead of pure whites we always get slight greys after development. This might not seem to be the case, but it becomes quite glaring when you look at the margins of a bleached and an unbleached print side by side (and once you do so, there is no going back).
The bleach is a chemical agent that reverses the effects of the developer, but the degree of that is inverse to the image density, so it has much greater impact on the image highlights than the shadows. That, in turn, makes it possible to brighten up the whites without reducing mid and dark tones (i.e., to compare it to digital editing, it’s similar to moving the levels slider on the high end toward the mid tones). The most common bleach is Farmer’s Reducer (recipe below), and it’s the only one I am familiar with.
Bleaching with Farmer’s Reducer has to happen on a fixed print before toning, and the print must be fixed again afterwards (before the toning). However, the bleach wrecks the fixer, so rather than using an expensive long lasting one like rapid fixer, it’s more economical to use plain hypo. It is generally recommended that the hypo is not kept longer than 24h once used, though I find that if I wash the print briefly before the second fixing, it will last 48h without issues (one should not worry too much about the fixer, as if it is not good it will be revealed when the print goes into the selenium toner, turning yellow, or even orange; it is, of course, possible to test this on a strip that has been processed alongside the print).
There are three basic ways in which bleaching can be used: overall, local and for retouching.
Overall Bleaching
The whole (wet, not as per Adams dry) print is immersed into the bleach for a short period of time for overall highlight reduction. This is the most fickle of the three uses, and it’s easy to destroy the print if things go wrong. The keys to success are: rapid, smooth insertion into the bleach, no agitation (con Adams, agitation will produce uneven reduction; if edges of the paper are rising too much they can be gently pressed down with tongs), and finally rapid removal followed by immediate immersion into a clean water bath with some agitation to kill the bleaching as fast as possible (use gloved hands and no dripping off the bleach in between, as this will produce streaking).
The bleaching effect can only be judged after about a minute in the water bath; if it’s not enough, it can go back into the bleach. There also tends to be further slight brightening when the print gets re-fixed, so it’s best to err on the darker side. (To say all of this can be nerve-wracking when you have spent hours working on a large print is an understatement, but it’s worth it, and it’s perfectly possible to control it well with a bit of practice and rigour in making up the solution.)
Localised Bleaching
Local bleaching can be used to brighten up specific areas of the print (the bleach is sometimes referred to as ‘liquid light’), a bit like dodging, except it only affects highlights. The bleach is applied using a brush, or, for larger areas, sponge. The wet print needs to be placed on an angled glass (steep enough to allow good water run off), and a small jet of running water is used to protect the areas below those being bleached by creating a water barrier that immediately washes away the running off bleach. Patience is a key, but as long as you don’t make the bleach too concentrated chances of wrecking the print are very low. Important point: when using a brush, the hair fixture must not contain any iron, as that will cause irreversible blue, cyanotype-like, staining (this can sometime emerge only after the print has dried).
Bleaching for Retouching
Bleach can be used to get rid off black flaws on the print (i.e., negative scratches and pin holes). To this end, a more concentrated bleach is applied by a sharp wooden point (toothpick or such) onto a dry print (this minimises the bleach seeping sideways) to reduce it back to white, which then can be retouched the normal way.
There are a couple of caveats. Firstly, the new white flaw will be much bigger than the original black one. Also, I find the pure black cannot always be fully reduced to white, so there is a risk of a white spot with a darker speck in the middle, which is very hard to retouch well, especially if the area is very light, so at times the fix might be worse than the original. If the print merits it, it is worth printing the offending bit on a couple of scraps of paper and test it out. And again, the brush used for the subsequent retouching should ideally not have an iron/steel fixture, though retouching is done with a brush that is nearly dry so you might get away with it.
(It is often more productive to scrape off the tiny black spot with a scalpel; the scalpel needs to have a rounded blade, e.g., no. 10 blade, not 10A, and it takes a bit practice. It is also worth noting that most defects of this type are pinholes, which are caused by rapid gas release from the emulsion during development; it is best to find a process that avoids that; I used to see these fairly regularly using Fomadon Excel (Xtol clone) and Ilford stop bath, but I see very few of them since I switched to using 1% acetic acid stop bath with no agitation and PyrocatHD, which has also eliminated most of the undissolved crystals that cause white spots on positives, particularly common on Foma films. But I am sidetracking.)
Recipes
These are my Farmer’s Reducer recipes. They are based on The Darkroom Cookbook (which every darkroom printer should have at hand), however the recipes there include potassium bromide, which IIRC makes it possible to re-develop the image if you over bleach it, but it is not necessary for the bleaching. The overall bleaching is the one that needs to be accurate for the timing based control to work, the other two are ad hoc, as we have visual control over what’s happening.
The hypo component is the standard plain hypo solution (240g of sodium thiosulfate per 1l water; full instructions per The Darkroom Cookbook). The potassium ferricyanide is dissolved separately and only mixed with the hypo immediately prior to use, as the complete mix has a very short life.
- Overall bleaching: 1.2g ferricyanide + 1l water + 120ml hypo; bleaching time ~30s @ 20C. Keeps long enough to bleach at least five prints. The rinse water should be changed between the prints. Using 3l of water gives enough solution to comfortably bleach 16x12 prints (not enough solution makes it hard to insert and remove the prints smoothly, which for this process is critical).
- Local bleaching: pale yellow (‘normal’ urine colour) ferricyanide solution + equal volume of hypo; keeps about 10min (basically looking for a similar, perhaps a touch weaker, concentration as above, but as only a small amount is needed, weighing the ferricyanide is not entirely practical).
- Retouching: lot more concentrated ferricyanide than above (well beyond oak matured chardonnay) — this is a big hammer solution. Test in advance what works for you.