Fogging redeveloper or separate fogging agent and redeveloper?

[Hans Borjes]

I am currently trying to adjust the intensity of a fogging agent in b/w reversal processing. For single use I have recalculated the amounts from a popular recipe and 520mg stannous chloride in 260ml water plus 2,9ml potassium hydroxide (45%) is still creating a precipitate.

Additionally it turns out that this is still too much fogging.

I wonder whether it would be possible to do the same that Kodak did in the Tmax reversal kit and add the fogging component directly into the second developer?

In my case this would mean to add a few (hundred) milligrams of stannous chloride into the Rodinal 1:25 working strength solution of 260ml.

Has someone an idea whether that would work, or would this destroy the fogging or developing capability?

 

[htmlguru4242]

Not sure, but the question here also may be "why use a fogging agent". Doing this with light is SOO much better, as it requires no additional chemistry and is believed by many to create superior, more archival results.

 

[Donald Qualls]

As I understand it, you want the fogging agent to fully fog the film -- any adjustments are made in the first developer; develop more there, and you'll lighten the final image because the silver developed in the first dev is removed before the reversal and second dev. Essentially, all the processes in B&W reversal after the first dev are carried to completion.

So, if your transparencies are too dark (which I infer from your statement that the fogging agent is too strong) you either need to first develop more, expose more, or put more halide solvent in your first developer (to clear highlights).

 

[Hans Borjes]

Not sure, but the question here also may be "why use a fogging agent".

I regret that this in not my question.

Doing this with light ... is believed by many to create ... more archival results.

Another user with professional background in motion pictures has once posted in this forum that there is no evidence for that.

I am not sure what I am supposed to 'believe'.

 

[Hans Borjes]

As I understand it, you want the fogging agent to fully fog the film ...

Yes and no. I am not using halide solvent additives in the first developer which is fairly strong already (Rodinal 1:13, i.e. 20ml concentrate, 10 minutes at 24°C and 75 rpm).

From earlier experiments I know that I need just the right amount of light for a perfect slide, currently trying to create that chemically.

Back to my original question: can stannous chloride be added to the second developer?

 

[Hans Borjes]

I wonder whether it would be possible to do the same that Kodak did in the Tmax reversal kit and add the fogging component directly into the second developer?

In my case this would mean to add a few (hundred) milligrams of stannous chloride into the Rodinal 1:25 working strength solution of 260ml.

Cool, it works. Although 210mg stannous chloride have created some precipitate that I have eliminated by filtration. So it seems to be just a matter of parameter optimisation, i.e. amount of stannous chloride needed and adjustment of the second development time.

 

[Gerald Koch]

Donald is right, in reversal processing the second development should go to completion. Any adjustment in the density of the slide should be done by changes in the exposure index of the film and by the amount of development in the first developer.

 

[Hans Borjes]

Cool, it works. Although 210mg stannous chloride have created some precipitate that I have eliminated by filtration. So it seems to be just a matter of parameter optimisation, i.e. amount of stannous chloride needed and adjustment of the second development time.

It works even better when 210mg stannous chloride is solved in 240ml water first and 20ml Rodinal is poured slowly into the solution. No precipitate, no filtration necessary, a simple workable reversal developer, just a tiny digiscale needed.

 

[Hans Borjes]

Update: I have tried to reduce the amount of stannous chloride in my second developer. 20mg is far too less and has only a marginal fogging effect. 50mg is almost strong enough. Best uniformity of second development seems to be at 70mg and 4minutes.

So I will stick to the approach of a reversing second developer because it offers the best workflow with the Jobo machine.

However, the slides are still slightly yellowish. I will follow your suggestion and try adding a halide solvent to the first developer and see what it does in this respect.