Reversal processing b/w:fogging developer and second developer

[guangong]

Instead of a second exposure to light I want to re-expose chemically but every written description is vague and unclear about whether the second developer is needed after a fogging developer is used. Foma's instruction sheet implies that the fogging simply replaces re-exposure while another source hints that using Kodak fd-70 replaces re-exposure as well as the need for a second developer. Anybody have practical experience replacing the re-exposure to light chemically? And what formula works best?

 

[Gerald C Koch]

It's very simple. When you come to the development of the positive image all that needs to be done is to develop all the remaining silver halide in the emulsion. The negative image has been changed so that it cannot be redeveloped AFTER the bleaching step. Re-development can be done by EITHER re-exposing the film to light and using a conventional developer OR by using a fogging developer. A fogging developer can be as simple as a solution of sodium sulfide. This would produce a sepia image while a conventional developer would produce a black one. The sepia image can be quite pleasing for certain subjects.

 

[Rudeofus]

There are fogging bathes, there are developers, and there are fogging developers. Fogging bathes won't develop film, but will bring it into a state where a developer will develop all silver halide to metallic silver. Typical example for such a bath would be the E6 reversal bath, which is usually based on SnCl2 or borhydrides. Some companies managed to combine the E6 reversal bath with the E6 CD, thereby creating a fogging developer for E6. Please note that you can't develop regular B&W film in E6 process, but some bathes can be used.

 

[guangong]

Rudeofus, thank you for the differentiation between fogging bathes and fogging developers. I find that remark very helpful. I have been processing 16mm tri-x reversal movie film (7266)in D-19 which requires a re-exposure to light. I used to process b/w slides years ago and now want to develop 120 format b/w slides. I am going to experiment with Kodak Fogging Developer 70 which is supposed to give b/w slides and not sepia without a second developer and see what happens. A roll of 120 is a lot cheaper to experiment with than 100' of movie film.

 

[Rudeofus]

Wouldn't it be even cheaper to test expose a standard roll of 35mm Tri-X, cut the exposed roll into ten test clips which you then develop?

 

[phildil]

As far as I know, regular 35mm / 120 Tri-x is intended for processing as negative, and is not the same emulsion as Tri-X reversal (TXR) movie film 7266. So the results would probably differ.

Until recently Kodak/Eastman sold a processing kit "T Max Direct Positive Kit" or similar name which contained all the chemistry for processing BW reversal, and which included a fogging 2nd developer rather than specifying a re-exposure step. Have a look online for details, you might find a datasheet with the formulations. Just an idea! I never used it myself - I use the conventional fogging method, it's simple.

cheers
phil

Wouldn't it be even cheaper to test expose a standard roll of 35mm Tri-X, cut the exposed roll into ten test clips which you then develop?

 

[flavio81]

Guangong,

I don't know if you're aware, but Foma sells a reversal development kit, ready to use.

However i think it requires fogging by light exposure.

 

[Gerald C Koch]

A bit of clarification. A fogging developer can be a conventional developer with a fogging agent added or it can consist of a fogging agent(s) used alone in suitably buffered solution. The fogging agent is usually sodium hydrosulfite, sodium sulfide, thiocarbamide or 2-thiobarbituric acid. For examples look at Kodak fogging developers FD-70 and FD-72.

 

[Rudeofus]

I finally found some details and formulas about this Kodak FD-70 and some other commercially packaged fogging developers. Given their composition these are unlikely candidates for self mixing, but if you can source the original packages you are ready for rock'n'roll.

 

[Gerald C Koch]

I finally found some details and formulas about this Kodak FD-70 and some other commercially packaged fogging developers.

Thanks. With my first post I couldn't remember the name of the particular sulfide toner T-19 to use as a fogging developer. When I have used it I particularly liked the sepia color of the slides. The images are less jarring than the stark black of regular developers.

 

[dr5chrome]

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