Reversal Processing

[Joe O'Brien]

I had a chemistry major walk into the darkroom today and ask me if I could help him get a black and white transparency from some fp4+ for a project he's doing with a physicist and a biologist. I told him I had an idea but I'd never done it before and I wanted to run it by some people, so, here I am. My plan was this:

Develop (regular time)
Rinse
Bleach (Potassium Ferricyanide 10g/100ml)
Rinse
Re-Expose
Develop (regular time)
"Stop" (we do a rinse cycle for this in the darkroom where I work)
Fix
Rinse
Hypo-clear
Wash
Photo-Flo

Does anyone know if this would be a viable technique? If it is, how long would I bleach for? And, would opening the developing tank for a minute or so under full room lighting be sufficient "Re-exposure"? I'm not looking to buy any other chemicals because as far as I know there is no money or other compensation coming to the darkroom budget from either of the scientists, or this student.

[wildbill]

http://www.apug.org/forums/google.ph...ums%2Fhome.php

there are a few articles on this if you search the box on your left.

ilford also has info on their site, at least they use to.

[Photo Engineer]

NEVER use a Ferricyanide bleach when intending to get a reversal image from a B&W film. You lose the image. You must use Dichromate or Permanganate! Also you must use clearing baths in the reversal process.

Good luck.

PE

[Joe O'Brien]

Thanks for the speedy responses guys,

@PE: What is a clearing bath?

[Photo Engineer]

A stop bath with sulfite present and intended to "clear" the film of any excess developer or bleach. See elsewhere on APUG or in Kodak instructions on this.

PE

[Joe O'Brien]

PE: Great, thanks a bunch!

[dr5chrome]

..you can send FP4 to us, we do it all the time, but it's not mandatory. dr5.com

[holmburgers]

Here is the procedure I have used (once), but it came out very well.

1. Dektol 2:1 + 5grams HYPO/L - 12 minutes, typical to high agitation.

2. Ilford Wash Sequence (5 changes w/ agitation, or thereabouts)

3. 2-part A/B bleach mixed right before use*, 1:1 - 5 minutes, high agitation
a) 1.4% Potassium Dichromate (0.7% in final solution)
b) 4% solution of 48% Sulfuric Acid (for a total of 1% concentrated sulfuric acid in final solution)

4. Ilford Wash Sequence

5. 10% Sodium Sulfite - about 4 minutes

6. Ilford Wash Sequence

7. Light exposure - unscientific, just inspected it under a 40 watt tungsten bulb and tried to shine as much light on it as I could for maybe 3 minutes or so.

8. HC-110 dil. B - 7 minutes

9. Ilford Wash Sequence

10. Kodak Fixer - about 4 minutes (shorter than average)

11. Final Wash, 15 minutes running water

*mixing before use, A/B style, isn't actually necessary with dichromate bleach. I borrowed this from a permanganate bleach formula before actually understanding it. Though mixing in this way might be safer.

I did a couple films: Delta 100 came out well @ EI 64, and TXP320 @ EI 160. Good luck!

Also, there's a thread called "reversal processing controls" or something like that, and I outlined a lot of points made by Haist in his book, and Wall & Jordan in theirs.

Your 1st dev should be "to completion", and in a fairly high contrast developer (print developers generally). Using the normal stated developing time for negatives will probably not result in pleasing positives. I recommend a dichromate bleach, which by all accounts is less trouble than permanganate. Also, a potassium dichromate bleach will last indefinitely, not true with permanganate. Use sodium sulfite to clear a dichromate stain, metabisulfite for permanganate (or so I've determined by trudging through many different formulas, and from insights from others)

I'm definitely not an expert on the topic, but hopefully that's helpful.

[railwayman3]

30 seconds with Google produced the "official" method:

http://www.ilfordphoto.com/Webfiles/...1220441194.pdf

[Chris Douglas]

I have had good results with plus x pan, using the formulas from Anchell's books. However, I had to under expose buy two stops the get best results. I shot the plus x at asa 500 and got good density in the transparancy.

If the film has been exposed at normal speed, maybe the pro labs know how to get good results. Good luck.

Best regards,
Chris