Direct Positive Reversal

John Esco

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Registered User
Continuing my experimentation regarding printing methods, something which I was thinking that can be done but never actually tried or search more in depth came up by chance when I read an online article abaou Direct positive Reversal. Loking for more infos, I found few YT videos about the process and that was it. I had to give it a try...
I reckon many of you have tried that before and you already know "how to" but I will leave here some infos abaout the way I've done the prints.
Firstly, all shots have been done using my Wista N45 (that's the only one I have anyway :)) ) & Fuji 210mm, one continuous LED light source and my beautiful patient dead roses.
The paper used is Kentmere Luster, 5x7 (trimmed to fit in my 5x4 holders).
Once holders loaded under red light, I took the shots (as described down below) and then returned into the dark room I devloped te paper following these steps:
1. developed in normal developer (I used Ilford PQ Universal) until the paper turs almost completely dark (1-3 mins.)
2. sinked in citric acid (1 teaspoon/100 ml distilled water) - approx. 30 sec.
3. sinked in hydrogen peroxide - 12% - the picture starts to bleach
*** steps 2 & 3 back and forth until the paper gets completely (or almost) white - last wash in citric acid
4. rinse in tap water (to clear the acid)
5. expose to normal white light for few seconds
6. developed the picture as I regulary do (dev, stop bath, fix, rinse)
Here's four shots I did last evening:
1. f/8 for 6 sec.
2. f/11 for 10 sec.
3. f/8 for 10 sec. - paper pre-flashed for 0.5 sec.
4. f/8 for 8 sec. - paper pre-flashed for 0.5 sec.
Still did not figure it out what's the best exposure time, yet, but pre-flashing definitely reveals more shadows. Got to go. Lots of things to try and paper to waste :)
 

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Ian Grant

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I think your choice of bleach won't work as it should, it's more usual to use acidified Potassium Permanganate or Sodium or Potassium Dichromate, and some have used Copper Sulphate in all cases these are used with a weak Sulphuric acid solution, or a stronger addition of Sodium Bisulphate.

Back around 1973 I went to a talk by a PhD student (from Birmingham School of Photography) on reversal processing, he was using FP4 to make reversal slides then making prints on Ilfobrom again by reversal. The print quality was stunning but the process very finicky and hard to control, made all the more laborious because it was before the introduction of RC paper so the waas steps were a lot longer.

There's a section on Direct Reversal on Unblinkingeye.

Ian
 

David M

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Ian,
That certainly sounds like a display of virtuoso printing, but I'm blowed if I can see the advantage of the double reversal. Did it give some special advantages that I don't know about?
Was it a demonstration to show how precise and versatile his system was?
 

Donald Qualls

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@Ian Grant This is one of the relatively recent developments in B&W reversal: use of peroxide and either acetic or citric acid to dissolve the developed silver. Much safer and more environmentally friendly than dichromate, and doesn't soften emulsion like permanganate (and no sulfuric acid required). You do (according to YouTube) have to avoid leaving the materials lying face up in the bleach, as the dissolved silver can redeposit leading to brown stains.

The hard part, depending where you live, might be obtaining 12% peroxide. In the USA, you can buy it on Amazon, but in EU or Australia it might be harder to come by. Worst case, you can probably get the 30% strength used in hair bleaching and dilute 2+3 with distilled water immediately before use.
 

Ian Grant

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David, the prints had amazing tonality, black and white reversal gives excellent sharpness and also finer grain. A reversal B&W slide has a longer tonal range than a corresponding negative made alongside, that shows in the prints as well.

Birmingham School of Photography was part of Birmingham Polytechnic and had a joints Student Union with Aston University on the main common campus site. So he was a fellow student and the talk was at a Photographic Society meeting. It was a talkto show what was possible but he highlighted how difficult it was to get consistent results as well.

The PhD student's research was sponsored by Kodak although he used Ilford products. It was really about whether the process could be simplified. At one time Kodak sponsored PhD students to do pure photographic research, Dr Mike Ware was another they sponsored and he was looking at alternative printing processes.

Donald, I've done commercial research into reversal processing for a London lab not so long ago so know what will give the best results, I spent a number of years as a photo/emulsion chemist, later switching to precious metal recovery and setting up an analytical lab.

The issue with Peroxide and Citric/Acetic acid is you aren't getting good Silver solvency, it's rather like the jewellery manufacturer's silver/gold bombing solutionss designed clean up castings here a weak solution of Cyanide is mixed with Peroxide. The castings need continuous contact with fresh mixed Cyanide/Peroxide as the Cyanide breaks down. This is an alternative to Cyanide stripping where the castings are the Anode in a cyanide bath it's similar to plating in reverse.

I mention the weak bonbing solutions because they are used for the same reasons a lot safer than a heated quite strong Cyanide stripping bath giving off fumes. But using Peroxide in combination with Cyanide or Citric/Acetic Acid have the same downsides.

Ian
 

Donald Qualls

New Member
Registered User
I won't say the peroxide/acid bleach gives results like permanganate or dichromate -- just that it does work, at least on prints (which is where I've seen it done on video), and uses less hazardous and less restricted ingredients (and also isn't prone to strip the emulsion if the baths are too warm).
 

Ian Grant

Well-Known Member
Registered User
If it's the videos I've seen I didn't think much of the print quality and I've seen way better early this year and in the past.

Ian
 
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