Lightening up too dark black&white reversal films

Perhaps others here also know the chronic problem of too-dark b&w reversal films. At least for me, b&w reversal films turn out much more often too dark than too bright. This happens especially in the case of expired films or obscure russian film stock etc., as well as in the case of negligence in development or lack of potassium rhodanide additive.

Often you just have a basic fog (so, bad Dmin) … There are many reasons.

The ambitious home laboratory man probably knows the “farmer’s reducer,” with which too dark prints can be spiced up and saved excellently. Unfortunately, you have to work here on sight, which is difficult with 15m / 50ft of film. Also, the mixed working solution lasts only about an hour and then has to be discarded.

I had an idea the other day and am thrilled with the result: If you use Part A of the reducer 1:10 diluted and use simple fixer as Part B and apply them separately one after the other, the solution last almost forever, and in addition, super even reduction over the entire length of the film can be achieved.

I’ve treated a dozen films and film leftovers with these solutions in recent days, all of which were “way too dark” and, in part, making sensational improvements. Depending on the film stock, the results are different, but “one stop brighter” always seems to be achievable, some films I’ve even been able to elicit a good 2 stops more light. Only an old Plus-X has lost a bit of blacks in the shadows.

Here are two examples:

Drastic a 50 ASA Svema, in which only weak contours were recognizable, even when projected. You can see by the light flares how much light I had to use while taking these pictures

The same image after 10 minutes of treatment

A less extreme example, a Plus-X exposed in 1999, that Kahl Film messed up in developing (base fog). Both images were photographed with identical settings, the top before, the bottom after 3.5 minutes of treatment

Yes, with such intense changes, there is some detail loss in the highlights, but the more important gray values are correct now. No chemistry in the world helps against Kahl’s streaks, of course.

Warning: The process is irreversible, if something goes wrong, it can no longer be corrected. But what is to go wrong when a film is already too dark anyway …

The recipe for a 1 liter working solution is simple (better make 2 liters for the Lomo tank).

Part A:

5g Potassium ferricyanide (Red prussiate of Potash)
8.5g Monopotassium phosphate

Both ingredients are available at Ebay or Amazon for little money.
Part B is a normal fixer solution.

Rough rule of thumb for Foma R100 at 20°C is “3:30 minutes per stop.”
Warning: After fixing, the film should be rinsed again. This also applies in case the first attempt (test strips!) was not yet sufficient, because fixation bath residues in Part A drastically shorten its durability.