Choice of Kodak reversal process

I have a question for anyone interested and in the know about reversal process developer chemistry. I have done a fair number of rolls using the reversal recipe in Kodak's old formulary from the 1940s, with D168 for 1st dev and D158 (1:1) 2nd dev.

Later Kodak literature (e.g. J-1 from 1973/77, right up to pamphlet J87 from 2003) specifies D67 for 1st dev, which is identical in composition to D168 but with potassium bromide – D168 is notable and quite unusual for having no restrainer in – and a fogging developer (which I can't get the ingredients for) or D19 for 2nd dev, which is D67 minus the thiocyanate halide solvent. I have also done a couple of rolls using this combo.

So D168, D67 and D19 are all the same basic recipe, namely D67 = D19 + KSCN; D67 = D168 + KBr. D158 is totally different from any of these (see below) and is listed elsewhere in the 1940s document as 'Velox Developer: normal-contrast developer for blue-black image tones on Velox and Gaslight papers'...

Can anyone comment on what differences these different compositions might make to the finished image (predominantly the question of restrainer vs no restrainer in the 1st dev, but also any possible difference between using D158 vs D19 for 2nd dev)? The baseline 1st dev time for D168 is 6 minutes; for D67 it's 8 minutes. I guess this extra time is because of the presence of the restrainer, but it will also mean the thiocyanate has more time to act. I would also be extremely interested to know the possible reasons for Kodak changing this formulation by adding the restrainer which perhaps is the same as answering the question of what difference it will make to the image...one assumes that they saw it as an improvement but in what way? Or perhaps just to accommodate newer film compositions?

I unfortunately do not have the time at the moment to do any side-by-side comparisons/tests in order to answer this question (new baby etc!), but basically am trying to decide whether to use D168+D158 or D67+D19 for any processing that I do manage to do! I like the results I got from both processes and as expected they're fairly similar but it's hard to compare when they were completely different shots.

Compositions are as follows (per litre):

D168 (older 1st dev)

Metol 2 g

Sodium sulfite 90 g

Hydroquinone 8 g

Sodium carbonate (anhydrous) 44.5 g

Potassium thiocyanate 2 g

D158 (older 2nd dev; recipe quantities halved because 1:1 dilution is specified)

Metol 1.6 g

Sodium sulfite 25 g

Hydroquinone 6.7 g

Sodium carbonate (anhydrous) 34.5 g

Potassium bromide 0.45 g

D67 (newer 1st dev)

As D168 plug 5 g potassium bromide

D19 (newer 2nd dev)

As D67 minus potassium thiocyanate

That D168 looks like a close relative of Dektol/D72, with the KSCN added. You could probably use Dektol diluted to give the right sulfite concentration (the D72 recipe is readily available) and add the thiocyanate -- that's used a lot in reversal. The D158 looks pretty generic to my eye.

The difference though is that D72 *does* have potassium bromide in it. Mainly my question was, what might the reason be for D168 not having any restrainer in it, and what effect will this have in practice for reversal development vs using D67 which is identical except for the addition of restrainer?

Films were a lot slower in the 1940s -- this process was likely intended for (old scale) ASA 25 or so, possibly even on glass plates (glass was used in projection for a good while because of its heat tolerance compared to early celluloid). Also, fog in the first developer isn't a problem for the final product, as it'll simply produce developed silver that will bleach away. The combination may have added up to restrainer not being needed until faster films came along (starting in the 1940s, for the most part).

Thanks, and this was one thought I'd had, knowing it is a 1940s recipe. I have had good results though with it, mainly using Rollei Retro 80S and 400S (better results with the 400S though!). The only issue I've occasionally come across is some odd bleaching look in very dense areas of the finished image, which I suppose could be a result of the absence of a restrainer since I'm fairly sure it's not caused by other problems in my process such as inadequate reexposure or 2nd development.

If your heaviest shadows aren't dense enough it's very tempting to suspect inadequate reversal exposure. It's easy enough to increase that, and there's no harm to be done by trying it -- you won't likely get enough exposure to go past the peak of the curve and start re-reversing the halide (even with old films, this mostly happened with the sun in frame, like Ansel's famous "Black Sun").

Hi Joseph, I saw your thread here and on facebook. I meant to reply earlier, but I didn't have Haist Vol 2 on hand to consult. BTW, congratulations on the new baby! Be sure to take lots of nice B&W chromes; they'll be priceless memories soon enough!

With regards to KBr in the first developer, essentially what Haist says is that fog will cause a lowering of Dmax in the positive, which makes total sense since it causes some of the silver halide to be used up. Antifoggants are especially required when using higher developing temperatures, although in this section he is discussing more powerful restrainers such as benzotriazole and 6-nitrobenzimidazole.

Haist's major contention is that reversal development is fundamentally a competition between "physical" and "chemical" development.

Chemical development is the "classic" development mechanism that occurs in all developers where a reducing agent reduces silver halide to metallic silver and in the process, itself becomes oxidized. This produces long filamentous metallic silver with high surface area and covering power. Chemical development is faster than physical development.

Physical development occurs by a different mechanism -- a silver halide solvent complexes a silver cation. The complex is unstable in the presence of metallic silver filaments and the silver cation is released from the complex, reduced to metallic silver, and deposited onto the filament. Reversal first developers contain silver halide solvents and lots of sulfite whose solvent action is catalyzed by the large surface area of chemically developer metallic silver. Thus, the most physical development occurs in the image locations where there is the most chemically-reduced metallic silver (i.e. the highlights), thereby using up the silver halides in those areas and giving clear highlights.

Potassium bromide is a restrainer, so it will repress fog (giving denser blacks in the final chrome) and it will slow the rate of chemical development. This gives the solvents more time to work on the silver halide, and allows you to adjust the balance between physical and chemical development.

So my interpretation is that if you are getting dense Dmax and clear highlights without KBr, there is little reason to add it to the process. If you are having problems with getting clear highlights, and extending development times just reduces Dmax and doesn't brighten the highlights, it may be beneficial to use a first developer with KBr.

In terms of second developer, I believe that by far and away the most important variables in reversal processing pertain to the *first* developer: composition, temperature and developing time. So I haven't given much thought to 2nd developers, although I wouldn't recommend using most first developers (i.e. ones that contain silver solvents) as second developers. Haist recommends D-8, D19 or D-72 (aka Dektol) as second developers.

Good luck!

I have a nice set of B&W slides I shot at night at the Seattle World's Fair in 1962. I haven't tried the process since. However, instead of worrying about about the fine points of a reversal process, have you considered the advantages of taking a perfectly normal B&W negative and contact printing it to litho film, developed in Dektol or equivalent? The advantages are that you can make slides from selected negatives instead of committing a whole roll to the reversal process, and you have far closer control over your results. Also, since litho film can be processed under a red safelight, the process is functionally much like making prints.

The ortho films I've seen sold in 35mm rolls are too fast for reasonable darkroom contact printing -- ISO 80 or so. The old Kodalith we'd have used for this kind of thing back in the 1970s came in large sheets (up to 16x20 at least), but not, AFAIK, in roll formats (modern equivalents come at least up to 8x10).

That said, nothing says you can't enlarge onto the litho film to produce much larger transparencies.