Kodak fogging redeveloper - dithionite

Raghu Kuvempunagar · Oct 5, 2020

Alessandro Serrao said:
I've got another question: do any of you guys have noticed that, when using a fogging redeveloper, all system must be recalibrated? That is, new first development time etc...
I've noticed it using thiourea as a second redeveloper. The slides came out incredibly darker and with much higher DMax than with light re-exposure.

It could be related to highlight clearing. Haist writes "When reexposure by light is part of the reversal cycle, some of the small or inert silver halide crystals are still present and must be removed by the thiosulfate of the fixing bath." It's likely that a powerful fogging redeveloper like Thiourea can reduce these halides which are not activated by light exposure and thereby produce darker slides. Maybe with suitable amount of cysteine (or thiosulphate) in the second developer, this can be taken care of and you need not recalibrate the first development. Something you can experimentally test and find out.

Rudeofus · Oct 5, 2020

Raghu Kuvempunagar said:
As I said earlier, in a well-designed formula, there is a good technical reason for including a component. PE has clearly said that for color slide film, halide solvent in second developer is there to promote dye formation and improve grain structure. But B&W reversal doesn't have to worry about dye formation. Isn't it?

I don't know, whether Ethylene Diamine has any effect on dye formation, but I can exclude this with certainty for DTOD. DTOD loves to bind with silver, but apart from that it is mostly inert. PE mentioned, that it is not biodegradable, because it is so inert. The differences between E-6 color developer and B&W reversal second developers may be rooted in technical details of these films. B&W negative films may have a straight (or at least monotonous) curve up to very high densities, which means it would be exceedingly hard to clear highlights in reversal. Therefore B&W reversal first developers don't even attempt to develop all the silver in those highlight regions, and expect the second developer to leave quite a bit of the silver halide undeveloped.

Raghu Kuvempunagar said:
As a matter of fact, Haist warns you against using them:

"If a first developer was used that did not contain an excessive amount of silver halide solvent, such as Kodak D-88, then the same developing solution may be used for the second development. Many first developers do contain sodium thiosulfate or potassium thiocyanate, and such solutions are usually unsatisfactory, often depositing a silver scum (dichroic fog) on the emulsion surface. The silver solvent in the developer results in a loss in the maximum density obtained in the positive image."

Excessive silver solvent in first developer certainly degrades DMAX, but I don't see how this would apply to second developer. The dichroic fog scare may also be a bit outdated, these days you have to put in a lot of effort to create dichroic fog in modern films.

DeletedAcct1 · Oct 5, 2020

Given that it's not possible to develop all the halides in the first developer, given that there must be no solvent in the second developer, in no solvent is used in the first developer at all, one can use a thiosulfate only bath after the clearing bath just to clear the highlights a tad by inspection?

Raghu Kuvempunagar · Oct 5, 2020

Alessandro Serrao said:
Given that it's not possible to develop all the halides in the first developer, given that there must be no solvent in the second developer, in no solvent is used in the first developer at all, one can use a thiosulfate only bath after the clearing bath just to clear the highlights a tad by inspection?

This is what some apug old timers did I believe. You can search for the thread that has Jordan and PE discussing the pros and cons of such an approach.

DeletedAcct1 · Oct 5, 2020

Raghu Kuvempunagar said:
This is what some apug old timers did I believe. You can search for the thread that has Jordan and PE discussing the pros and cons of such an approach.

I've just received an answer from Bellini Foto. Its redeveloper is most probably based on dimethylamine borane or tert-butylamine borane. If it's the cae, what specific precautions I have to follow to handle it?

Raghu Kuvempunagar · Oct 5, 2020

Alessandro Serrao said:
I've just received an answer from Bellini Foto. Its redeveloper is most probably based on dimethylamine borane or tert-butylamine borane. If it's the cae, what specific precautions I have to follow to handle it?

No idea as I have never used borane. Doesn't Bellini's MSDS tell you what precautions to take with their chemistry?

Rudeofus · Oct 5, 2020

Alessandro Serrao said:
I've just received an answer from Bellini Foto. Its redeveloper is most probably based on dimethylamine borane or tert-butylamine borane. If it's the cae, what specific precautions I have to follow to handle it?

Judging from the MSDS of this compound it is extremely unlikely that anyone could legally sell it to you. I recommend you use Stannous Chloride for chemical reexposure, which you can get from Suvatlar.

Rudeofus · Oct 5, 2020

Alessandro Serrao said:
Given that it's not possible to develop all the halides in the first developer, given that there must be no solvent in the second developer, in no solvent is used in the first developer at all, one can use a thiosulfate only bath after the clearing bath just to clear the highlights a tad by inspection?

It is quite easy to develop "all the halides" in the first developer, but such a first developer would be foggy enough to kill all the DMAX.

DeletedAcct1 · Oct 5, 2020

Rudeofus said:
It is quite easy to develop "all the halides" in the first developer, but such a first developer would be foggy enough to kill all the DMAX.

When you write "to kill all the DMAX" do you mean also density around the sprocket holes?
I've downloaded the reversal process from Orwo:
http://www.filmotec.de/wp-content/uploads/2010/08/V-I-VV-4185.pdf
http://www.filmotec.de/wp-content/uploads/2010/08/V-I-VV-4186.pdf
I've understood that:
1) some kind of silver solvent (thiocyanate, thiosulfate od DTOD) is mandatory in the first developer;
2) every professional recipe I've stumbled on require a light re-exposure, even the original Scala processor do that. Does that imply that a fogging redeveloper isn't suitable for b&w reversal?

Rudeofus · Oct 5, 2020

Alessandro Serrao said:
2) every professional recipe I've stumbled on require a light re-exposure, even the original Scala processor do that. Does that imply that a fogging redeveloper isn't suitable for b&w reversal?

The formulas posted by Jens Osbahr use Stannous Chloride for chemical reexposure.

Raghu Kuvempunagar · Oct 5, 2020

Alessandro Serrao said:
every professional recipe I've stumbled on require a light re-exposure, even the original Scala processor do that;

DR5 doesn't use light rexposure. His DMax could be high because he uses chemical fogging. However, he can get clear highlights even without a halide solvent in the first developer which is a tall feat considering he can process films like TMax 100 and 400.

Raghu Kuvempunagar · Oct 5, 2020

Alessandro Serrao said:
Does that imply that a fogging redeveloper isn't suitable for b&w reversal?

You can settle this light reexposure vs fogging redeveloper issue by picking a film of your choice, shooting 3 rolls of identical scenes, sending one roll to DR5 for processing, one to Studio 13, and process the third in your best light reexposure based reversal process. And then compare the three objectively (DMin, DMax, speed, clear highlights, grain, shadow details, sharpness, etc).

doctorpepe · Jan 18, 2023

So to process monochrome reversal films, I have access to both 2-thiobarbituric acid (For FD-70) and L-Cysteine HCL (For FD-72). Any reason to not use small amounts of both in the formula, or one over the other?

Rudeofus · Jan 19, 2023

I have never experienced Thiobarbituric Acid (or anything containing the word "barbituric" in its name), but people told me, that Pyrimidine is one of the foulest smelling compounds in a regular chemistry lab. Cysteine is a silver solvent at higher pH, so formulate your brew carefully.

doctorpepe · Feb 2, 2025

I know this thread is older but I was hoping not to reinvent the wheel. I’m getting excellent results with Ilford PanF+, Fomapan R and Ilford Hp5+ using a modified Agfa D-1 for the PanF and Fomapan and D-72 or D-11 for the HP5+. All first developers have thiocyanate, with the amount added to suit the film & developer. Dichromate bleach & have been using light reversal and 2nd develop in D-72. Now my question.

I have used the Kodak FD70 & FD72 as second fogging developers without light expo (obviously not needed!) but…I don’t necessarily like a sepia image. Has anyone tried using Benzotriazole with any fogging developers without light to cool the image more towards neutral? Another option might be to gold tone the sepia image to move it towards blue or purple but I haven’t tried it (I have Gold Chloride so I could try it if I have an image worth of post treatment in gold).

If not, I will probably try both the Benzotriazole and maybe the gold toning anyway but I would appreciate hearing from anyone who has any info in this before I spend extra time in the darkroom.

Stay well & take more pictures (on film).

Donald Qualls · Feb 4, 2025

Do the FD70 and FD72 formulae contain thiourea and produce silver sulfide (like sepia toner)? If so, gold toning may not work, and benzotriazole won't make any difference. A regular developer like D-76 with stannous chloride added (or a separate stannous chloride fogging bath) will produce a silver image that ought to resemble what you get with light exposure and conventional second developer.

Kodak fogging redeveloper - dithionite

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