Large format direct positives B&W

George Collier

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Greetings - I have a friend doing very creative work in a graduate program, and among other things, is using an 8x10 view camera to shoot Ektachrome transparencies, a pricey endeavor. He would like to do some with a B&W film / process.
In his search for this, he has seen some info on the Ilford web site, including info for self mixing, including the use of sulfuric acid, which has concerned him a bit, due to potential handling issues.
I remember the old Kodak direct positive kit, back in the 70's used with Panatomic-X, as I remember, which I don't think is any longer available.
Any suggestions for him? He is quite energetic and smart, so some level of work and difficulty will not be an issue (he processes his Ektachrome himself).
 

koraks

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So he can learn to safely handle the sulfuric acid; no problem there at all.

Does he want to do transparencies or direct positive prints on paper? Both are possible. I'd recommend starting with the latter to get a grip on the overall process. Reversal processing isn't too difficult in principle; the trick is to control contrast. Lots of trial & error involved. The chemical steps aren't too complicated. Risk of harm is really, really minimal if he observes some basic safety & sensibility measures.
 

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Raghu Kuvempunagar

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George Collier said:
In his search for this, he has seen some info on the Ilford web site, including info for self mixing, including the use of sulfuric acid, which has concerned him a bit, due to potential handling issues.
Click to expand...

Adox Scala Reversal Kit, Foma Reversal Kit, and Bellini Reversal Kit can be looked at.
 

blee1996

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I have not tried it myself, but from my understanding you can use Ilford FP4+, Delta 100, Rollei Ortho 25 (all available in 8x10 sheet size) for direct positive. I would also start with a reversal kit to get a feel for the process, before mixing own chemicals.
 
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George Collier

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Thanks for the comments and suggestions. He wants a direct positive (transparency) result from shooting film, whether the film is intended for Positive or negative. Any path to a final B&W positive transparency.
 

MCB18

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Raghu Kuvempunagar said:
Astrum sells a direct positive film. Check with @MCB18 who might have more info/experiences to share.
Click to expand...
Hi! Not in LF, but in 35mm. Honestly I’m a bit underwhelmed by it, it’s a cool film for sure but my god the slides are super thin…

I do have a direct positive film from Kodak, it’s film 2422 and it comes in giant 9.5” rolls. And it works really well! The downside is that it’s SLOWW, as in, the best results I’ve seen thus far come from @gezak22 who got a speed of 0.4 ISO after processing it in Rodinol 1+25 for 30 minutes.

I’m absolutely willing to cut some of this film into 8x10 (when I have a spare few hours over the weekend) for your friend if he wants some, just let me know!
 

MCB18

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Oh, here’s an example of the film. Direct negative enlargement, turned out very well.
 

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Ivo Stunga

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No special film needed to pull this off - it's the processing that turns BW film into BW slide. I do however recommend looking for a PET base for extra clear/crispy slides.
 

Lachlan Young

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Standard issue B&W reversal processing on 8x10 sheet film will do the job. All the relevant materials are on PET clear base, so you'll get good highlights.
 

MCB18

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Last edited:

MCB18

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Lachlan Young

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George Collier said:

MCB18 and​

Lachlan Young​

Thank you for the responses. Can you say more about the direct processes (chems, etc) or point to where info is?
Click to expand...

Start with the Foma or Adox kits, however handling Sulphuric Acid is fine if done in an appropriate environment wearing appropriate PPE. The acidified permanganate bleach is preferable to the old dichromate bleach, but do not use first developers containing potassium thiocyanate with permanganate bleaches.
 

koraks

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Lachlan Young said:
The acidified permanganate bleach is preferable to the old dichromate bleach
Click to expand...
From an environmental and healthy & safety perspective, yes. From a technical perspective, not per se. I think many people (including myself) have experienced that dichromate bleaches tend to be a little more robust, stable, less likely to damage the film and overall easier to use. But...hexavalent chromium. Someone hesitant to handle sulfuric acid surely would balk at using this.

MCB18 said:
I believe that he has already discounted this method due to not wanting to handle sulfuric acid.
Click to expand...
In this case, painting oneself into a corner really is a choice, and one I already recommended steering clear of.
 

Ivo Stunga

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Acids aren't that dangerous with simple acid-safe gloves and a pair of cheap safety glasses. And you can make a larger volume of working solution to reduce one's exposure to concentrates. At least you can see where the spillage is.
 

isaac7

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Photo Engineer felt that dichromates were safer than permanganate. He felt that the risks of dichromates were easily mitigated while he worried about how strong an oxidizer permanganate is. He was also very worried about accidental combinations with other common darkroom materials. He didn’t mind having dichromate in his house but said he wouldn’t have permanganate in it.

Safety is a difficult thing to quantify. Clearly all three of the chemicals being discussed need to be handled with care. I haven’t tried B&W reversal processing myself but I am interested. Reading the different discussions here makes it seem like good results are certainly possible but it does take quite a bit of testing to nail the process as compared to negative development. If (when?) I try my hand at it I will most likely do it with the hydrogen peroxide/EDTA bleach that has been discussed.

A Better Black and White Reversal Bleach with Hydrogen Peroxide

In a previous post, I described how to develop your own black and white slides using a simple bleach based on hydrogen peroxide and vinegar. This post is about an improved bleach that has a number of advantages over that one. There are a lot of patents out there from the 1970s through the late...
imager.ie

If I couldn‘t get that to work I’d just go the dichromate route with a reducing agent like citric acid to least make the waste less toxic.
 
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