Redeveloping negatives

rrocap

rrocap

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Hi!
Is it possible to bleach and redevelop a negative? Can you change contrast by changing the developer or dilution of the first developer? Does it make sense at all??

Ricard
 
Did you mean to link to reversal processing? Not possible once the film has been fixed.
I read that slight increase in contrast may be possible, but I don't know how that works and toning is preferred for that. Decrease in contrast is definitely possible.
 
Yes, you can bleach and redevelop, but to change the contrast characteristics you usually bleach and redevelop in chromium intensifier to increase thickness and contrast. It is very difficult to consistently decrease contrast in redevelopment and any silver you lose when you re-fix is fixed and removed and can’t be recovered. A bleached negative can’t simply be developed 20% less to obtain the same result as developing the camera film 20% less. Partial blaching works better there, or to decrease contrast in printing, dye dodging with crocein scarlet was the standard approach. Dye dodging is difficult with 35mm film because of the small area and lack of a surface suitable for retouching.

These are desperate moves when you have a verifiable film photo of a UFO or the Kennedy assassination or a sasquatch/yeti/yowie, but which is that is underexposed. That’s no reason not to experiment with it, but exposing and developing well in the first place makes a lot more sense.

Marty
 
Not a redevelopment process, but making a manual unsharp mask and sandwiching with the original negative will reduce contrast, and increase edge sharpness.
 
retinax said:
Did you mean to link to reversal processing? Not possible once the film has been fixed.
I read that slight increase in contrast may be possible, but I don't know how that works and toning is preferred for that. Decrease in contrast is definitely possible.
Click to expand...
Yes, I did. If the thread starter is referring to negs that have already been fixed—perhaps he could have asked a less ambiguous question.
 
Hi guys.
Thanks for the answers.
The thing is that I have my times and dilutions on a notebook. I don't know what I was thinking and used hc110 1+63 with the dev time for 1+31 instead. I'm trying to boost contrast and then I remembered Tim Rudman talking about prints bleached and redeveloped with a contrastier developer. I assumed that maybe it can be done with negatives. Maybe use a selenium bath??

Thanks for helping! :)
 
rrocap said:
Hi guys.
Thanks for the answers.
The thing is that I have my times and dilutions on a notebook. I don't know what I was thinking and used hc110 1+63 with the dev time for 1+31 instead. I'm trying to boost contrast and then I remembered Tim Rudman talking about prints bleached and redeveloped with a contrastier developer. I assumed that maybe it can be done with negatives. Maybe use a selenium bath??

Thanks for helping! :)
Click to expand...

Conventional bleach and redevelop will not help. The silver that was not exposed was fixed - i.e. it is gone. You can try chromium intensifier - it ‘bleaches’ the negative but adds density to the silver that is there, which, when you redevelop will provide a thicker, contrastier negative. Don’t expect miracles:
https://www.digitaltruth.com/data/formula.php?FormulaID=33

Marty
 
Thanks for the link. Isn't it crazy how many photographic applications chromium bichromate has? Too bad it's so poisonous.
 
retinax said:
Thanks for the link. Isn't it crazy how many photographic applications chromium bichromate has? Too bad it's so poisonous.
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Indeed you need to take care with 6+ chromium as occurs in chromium dichromate. Considering that the alternatives use mercury chloride or uranium nitrate, this is one case where chromium is the low toxicity alternative. I routinely work with much more toxic substances, and with appropriate handling and disposal it is not unnecessarily hazardous.

There are three lower toxicity alternatives. Strong selenium toner gives you 0.5 grade increase in contrast. Bleaching and redeveloping in a staining developer gives about 1 grade contrast increase. Bleaching in farmers reducer and redeveloping in sepia toner can give you 2.5 grades difference. All these processes provide less increase in density and contrast than full intensification in chromium intensifier.

Marty
 
Freakscene said:
Bleaching in farmers reducer and redeveloping in sepia toner can give you 2.5 grades difference.

Marty
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Good to know, I keep that around anyway, might try it with some problematic negatives! Somehow Selenium is more often mentioned. Does direct polysufide toning also work? I suppose it does, but to the same degree?
 
retinax said:
Good to know, I keep that around anyway, might try it with some problematic negatives! Somehow Selenium is more often mentioned. Does direct polysufide toning also work? I suppose it does, but to the same degree?
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Polysulfide gives you about the same density increase as selenium. It won’t redevelop a bleached negative - you tone the negatives, re-wash, use wetting agent and dry.

Marty
 
Freakscene said:
(...) Bleaching in farmers reducer and redeveloping in sepia toner can give you 2.5 grades difference. All these processes provide less increase in density and contrast than full intensification in chromium intensifier.

Marty
Click to expand...


By "sepia toner" you mean thiocarbamide (aka thiourea) toner?

2.5 grades sounds like a substantial intensification. What would be the proportions, respectively of thiocarbamide and sodium hydroxide, to achieve that amount of intensification? Would the color of the intensified negative interfere with VC filters; I mean strong yellow stain means highlight regions pass no blue light, hence decreased contrast.
 
BernardL said:
By "sepia toner" you mean thiocarbamide (aka thiourea) toner?

2.5 grades sounds like a substantial intensification. What would be the proportions, respectively of thiocarbamide and sodium hydroxide, to achieve that amount of intensification? Would the color of the intensified negative interfere with VC filters; I mean strong yellow stain means highlight regions pass no blue light, hence decreased contrast.
Click to expand...

Thiocarbamide toner. I used Kodak Sepia toner mixed as per bottle instructions, so I’m not sure on proportions - I only did this once. The colour absolutely interferes with VC filters. For difficult negatives that you absolutely have to print, have grade 5 graded paper (if that exists) and be prepared to work hard. I never found the ‘hard’ developers very useful for contrast increase - Tetenal Dokumol added about half a grade but it probably isn’t made anymore. Dr Beers and the others never seemed ‘harder’ than Dektol.

Marty
 
Freakscene said:
Polysulfide gives you about the same density increase as selenium. It won’t redevelop a bleached negative - you tone the negatives, re-wash, use wetting agent and dry.

Marty
Click to expand...

Really, polysufide doesn't redevelop bleached film? It does redevelop paper.
 
retinax said:
Really, polysufide doesn't redevelop bleached film? It does redevelop paper.
Click to expand...

If you mean polysulfide like the original Agfa Viradon or Kodak Poly Toner with polysulfide and selenium, it doesn't redevelop bleached negatives very well. Later versions of Viradon or Kodak Brown Toner just with polysulfide redevelop better. The problem here is names and what they mean vary. This happens a lot.

Marty
 
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