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Black and White Reversal Techniques

Pretty straightforward stuff, actually.

First, a quick overview. Black & White negative process is easy: sensitized silver halide (generally a bromide) is exposed to light. It then gets treated with a developer, which converts the silver halide molecules to metallic silver where light has struck them, and leaves them as silver halide where light has not struck them. Then, the fixer (like ammonium thiosulfate, a rapid fixer) dissolves away the undeveloped silver halide, leaving the metallic silver behind. What we now have is a negative; "light" parts of the image are rendered as opaque metallic silver, and "dark" parts of the image are rendered as clear film.

But what if... we removed just the metallic silver and left the undeveloped silver halide?

That's what the reversal process entails.

My removing the metallic silver, undeveloped silver halide is all that's left on the film. Since it is undeveloped, that means it was not exposed to light originally... so the easiest way to turn it into metallic silver (and then proceed to a positive image) is to open the developing container and flip on the white light. Hold the reel near the light for a bit (probably in a water bath, so the gelatin doesn't crack), and then redevelop. VOILA... a black and white transparency.

It's the bleach that's tricky. I must have spent almost a month trying to track down a bleach.

It wasn't listed in library books, and nobody on talked about it very often, other than "buy the Photographer's Formulary or Kodak's TMAX Reversal kit.

I'm not overly keen on Kodak; so I wanted to see what I could do about finding a bleach.

Here's what I scrounged up:

In 1988, Hans Dietrich wrote an article describing a reversal process for Kodak TMAX films. It is available online, here. In it, he describes the two following bleach/clearing bath combinations:

This is enough for 5 rolls of film. Fritz Brown suggested on that 55g of sodium bisulfate can be used instead of the sulfuric acid. Use 1 part each solution A and B as a one-shot. This is enough for 10 rolls of film.

Other very important notes

According to Mr. Dietrich, the first developer MUST have a silver solvent in it. He suggests a variant of D76, or D-19 with 5g/L of Potassium thiocyanate. I believe that ANY developer with 5g/L of Potassium thiocyanate should work; however I have not yet tested this and your mileage may vary.

Reversal procedure

Finally, a quick rundown on the whole process.

    Reversal processing Black and White materials
  1. First developer (the suggested time in the Dietrich article is a little bit of a push compared to negative development; 10 mins is recommended; 9 mins is "normal" for negatives, and 11 minutes is a 2 stop push for negatives. Accordingly, you may wish to overexpose your film (1 stop), overdevelop (1 stop), etc to compensate for the reversal process.)
  2. water rinse for 1 minute
  3. bleach, 3 minutes (5 for permanganate bleach)
  4. water rinse for 1 minute
  5. clearing bath for 1 minute (2 minutes for metabisulfite bath)
  6. second developer (paper developer for 3 minutes is fine)
  7. stop bath (or water rinse, if you're like me)
  8. fix
  9. wash
  10. rinse (wetting agent?)
  11. hang to dry

Practical Experience

I've shot a few test rolls now, and reversal processed them. The silver solvent in the first developer is NOT necessary. I have been using Rodinal as the first developer; Generally, my processing temperature is around 16°C (that's 60-61°F). For time, I add one minute to the 18°C (68°F) time for intermittent agitation (inversion/small tank) and throw the tank on a motor base for continuous agitation. Using this technique, I get nice transparencies with about 2 stops increase in film speed (that is, rating APX 100 at 400, APX 25 at 100, etc). Of course, plan for inconsistencies and bracket as much as possible, plus and minus 2 stops (-2, -1, 0, 1, 2) if you can. I usually open the processing drum as I'm dumping out the first rinse water and leave it open the rest of the way through; once first development is done, light is desirable.


In case you missed these above... the article describing the bleaches and corresponding clearing baths is published online here.

I just found a collection of information on reversal processing here.

There is another article on reversal processing here.

Photographer's Formulary is a supplier of bulk chemicals and kits for photographers.