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Direct Positive process for B&W

 
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disemjg



Joined: 10 Jan 2002
Posts: 469
Location: Washington, DC

PostPosted: Mon Mar 24, 2008 1:55 am    Post subject: Direct Positive process for B&W Reply with quote

OK, so here is a question from way out in left field. Years ago Kodak offered a processing kit to produce B&W transparencies. Unsurprisingly such an item is no longer to be found. Does any one know how to replicate the process? I seem to remember that Kodak recommended Panatomic-X, which is also long gone, so some experimentation with films would be in order once the chemistry questions are answered.

I want to try the B&W reversal film with a Stereo Realist, just for fun.

John
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clnfrd



Joined: 26 Mar 2002
Posts: 616
Location: Western Kentucky Lakes Area

PostPosted: Mon Mar 24, 2008 11:59 am    Post subject: Reply with quote

It appears the necessary chemistry is still available by special order: http://www.bhphotovideo.com/bnh/controller/home?A=details&Q=&is=REG&O=productlist&sku=123359

Fred
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PhG



Joined: 11 Jul 2007
Posts: 11
Location: Paris (France)

PostPosted: Mon Mar 24, 2008 12:38 pm    Post subject: Reply with quote

Foma also!
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disemjg



Joined: 10 Jan 2002
Posts: 469
Location: Washington, DC

PostPosted: Mon Mar 24, 2008 1:00 pm    Post subject: Reply with quote

Thanks, that is just what I'm looking for. I did not even think of looking at the B&H web site, since I thought it would be too specialized for them.

I did not find it at Freestyle, which surprised me.

And the Photographer's Formulary site looks like fun, also.

John
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David A. Goldfarb



Joined: 03 Sep 2004
Posts: 142
Location: New York City

PostPosted: Mon Mar 24, 2008 5:02 pm    Post subject: Reply with quote

I think there's also an article on B&W still film reversal processing on unblinkingeye.com. You might also search for info on movie film reversal processing, which is a similar process (the main difference being handling long rolls of 8mm or 16mm film).
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clnfrd



Joined: 26 Mar 2002
Posts: 616
Location: Western Kentucky Lakes Area

PostPosted: Mon Mar 24, 2008 5:47 pm    Post subject: Reply with quote

I remember doing black and white 35mm slides for a TV station in the '50's that did not use anything but chemistry( no re-exposure to light.) This film was developed in a tyrpical roll film tank. I also processed B&W 16mm film that would run the film through a 1st developer...then through a bleach bath ...pass it by a small lamp to reverse it...then into a second developer then hypo, etc.. So there were two different processes. Fred.
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clnfrd



Joined: 26 Mar 2002
Posts: 616
Location: Western Kentucky Lakes Area

PostPosted: Mon Mar 24, 2008 6:18 pm    Post subject: Reply with quote

I've been picking my old, over-the-hill brain and it's all coming back to me. You can use any B&W film to make positive transparencies. You develop the film as you normally would. Then, you use a bleach bath to remove only the developed crystals, leaving the remaining unexposed light-sensitive crystals still on the film. Then you expose the film briefly to a light source. Next, develop it again in the same developer and use rinsing and hypo fixer as you normally would, and presto!! a positive image. This can be done with any film and your regular film developer. The only rub is, I don't know what the properties of the bleach bath are. That, I assume, will be included in a kit. Fred.
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Stephen Furley



Joined: 11 May 2001
Posts: 79
Location: London, England

PostPosted: Sun May 25, 2008 8:43 pm    Post subject: Reply with quote

Ilford have a .pdf file of a black and white reversal process on their website here:

http://www.ilfordphoto.com/applications/page.asp?n=90&t=Developing+Black+and+white+film

I used to use a slightly modified version of this with Agfa Scala.

If using normal negative film slow films tend to work better than faster ones.
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Mon May 26, 2008 1:46 am    Post subject: Reply with quote

You can get the same stuff as B&H at the maker's website

http://www.photoformulary.com/DesktopModules/StoreProductDetails.aspx?productID=77&tabid=9&tabindex=2&categoryid=0&selection=0&langId=0&Search=rev

It's 25 cents more than B&H but you won't have to wait a month to get it, and the shipping may be cheaper
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disemjg



Joined: 10 Jan 2002
Posts: 469
Location: Washington, DC

PostPosted: Sun Jun 01, 2008 3:29 pm    Post subject: Reply with quote

Thanks, Stephen. That Ilford PDF is a gold mine; now I'll have to track down the chemistry.

John
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Stephen Furley



Joined: 11 May 2001
Posts: 79
Location: London, England

PostPosted: Sun Jun 01, 2008 4:40 pm    Post subject: Reply with quote

I can't help you with a supplier in DC; in London Silverprint would have almost everything required.

Just about any print developer could be used; I used ID-78. Just about any fixer can also be used, I used Hypam, and I recommend the addition of the hardener, or the use of a hardening fixer, unlike with conventional negative processing. The sodium Thiosulphate which is added to the developer needs to be the pure compound, not a thiosulphate based fixer. If you know of anywhere that sells supplies for home brewing and winemaking, they should have Sodium Metabisulphite, this can be used in place of the potassium compound. I used a dichromate bleach rather than the permangamate one. Hardware stores used to stock permangamate, but I don't know if they still do, and it might not be pure. You're probably going to need a decent photographic or chemical supplier to get these.

The first development is the only really critical part of the process; the other steps are just carried out to completion, so leaving the film in longer than necessary, within reason, shouldn't do any harm. During re-exposure avoid overheating, and drying out, the film. The re-exposure can be replaced by a chemical fogging agent, as is used in the E6 colour process, eliminating the need to remove the film from the tank for re-exposure, but the chemical required is used in tiny quantities, and is difficult to obtain.

The Photographer's Formulary could probably supply all of the raw chemicals which you need, except possibly the sulphuric acid; sending corrosive liquids by post tends to be problematical, and expensive, due to the packaging required. Since you only need a small quantity you could try asking the chemistry department of a local school or college if they could let you have some. Remember, always add acid to water, never water to acid.
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