Can Kodak D76 be substituted for D94a by adding sodium thiosulphate?

Discussion in 'B&W: Film, Paper, Chemistry' started by mr.datsun, Feb 6, 2013.

  1. mr.datsun

    mr.datsun Subscriber

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    I read a post (not this forum) about the similarity between D76 and D94a. It said that they are very similar but that D76 is stronger. It then said to get something like D94a, to add 1L of a 10% solution of sodium thiosulphate to 1L of the D76. I'm no chemist but I looked at the two formulae and thought that they looked a bit different in terms of relative quantities of components.

    Simply put I want to try d94a for tri-x reversal processing but I cannot go through the process of mixing it from scratch at home. I thought that adding sodium thiosulphate to some D76, would be within the scope of my knowledge and resources, though. And I'm also dead keen on sticking to a potassium permanganate based bleach which I believe fits in with the sodium thiosulphate in the dev.

    Any view on a simple path to D94a, please?
     
  2. henry finley

    henry finley Member

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    Sodium Thiosulfate??? Where are you getting your info? That's fixer. Like adding kerosene to a vodka and orange juice. Never heard of D94a in 45 years of photography.
     
  3. brucemuir

    brucemuir Member

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    Henry, the formula for reversal 1st developer calls for adding some sodium thiosulphate to clear highlights but Mr Datsuns recipe in the OP seems way excessive.

    Sorry I'm also unfamiliar with D94a
     
  4. henry finley

    henry finley Member

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    Oh, my bad. Did not pay attention to the "reversal" part. Never did any reversals of monochrome film. Sorry.
     
  5. mr.datsun

    mr.datsun Subscriber

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    You mean a 1L of a 10% solution is excessive? That's just as I remember reading it. I see that D94a has Sodium Sulfite (anhydrous) 60.0 g in it. I'm a bit out of my depth with chemistry.
     
  6. Gerald C Koch

    Gerald C Koch Member

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    The first developer for a BW reversal process usually contains about 6 g/l of sodium thiosulfate to clear the highlights of the slides.
     
  7. mr.datsun

    mr.datsun Subscriber

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    brucemuir, If we assume that 10% means W/V then doesn't it look like a reasonable amount as by the the time you add 1L of it to 1L of D76 you have 5% W/V of sodium thiosuphate?
     
  8. mr.datsun

    mr.datsun Subscriber

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    Gerald, Thank-you. So what I need to work out now is whether D76 is similar enough to D94a once the sodium thiosulfate is added to produce similar results? I'll find the formula and post them.

    Kodak D-94A

    Water, 50 degrees C (125F) 750ml
    Kodak ELON (Metol) 0.6g
    Sodium Sulfite (anhydrous) 60.0 g
    Hyrdoquinone 20.0 g
    Sodium Bromide 7.0g
    DTOD 0.42g
    Sodium Hydroxide 20.0 g
    Water to make 1.0 L

    afaik, DTOD is the hypo for which we use the sodium thiosulphate.

    Kodak D76

    Water 750ml
    Metol 2g
    Sodium sulfite (dessic) 100g
    Hydroquinone 5g
    Borax 2g
    Water to make 1000 ml

    how does that look? Are the two similar enough? The quantity of Hydroquinone are quite different.

    I'm trying to get a result as like D94a as possible because I like what i've seen.
     
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  9. Tofek

    Tofek Member

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    The differences in the formula make the differences in the action of the developer : D-94 is a high contrast developer well suited for bw reversal whereas D-76 is a rather low contrast developer, thus not well suited for bw revereal.
    In effect, the amount of hydroquinone which is responsible for high densities on the film, is too low in D-76. What's more, there isn't any sodium hydroxide, which as a strong alkaline buffer removes fog strongly and contributes to high contrast. So using D76 you will end up with a grey positive.
     
  10. mr.datsun

    mr.datsun Subscriber

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    Tofek, thank-you. That's a very clear explanation! So I guess D94a has to be mixed from scratch? I'll stick to PQ Universal for the time being. I have ordered some sodium thiosulphate to add to it.
     
  11. Tofek

    Tofek Member

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    A good alternative to D-94 is the high contrast developer D-19, which you can buy, and add thiocyanate (or thiosulfate) if you want. On this site there is a comparaison of developers tested on Tri-X (see 'research') : www.super8.nl
     
  12. Gerald C Koch

    Gerald C Koch Member

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  13. mr.datsun

    mr.datsun Subscriber

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    Tofek, I hadn't seen that page. It's interesting if a bit inconclusive at times in terms of specific info etc. Test 1 doesn't say what film but I assume that like Test 3 it's also Tri-X.

    But aren't all the Test 1 results with Tetenal Dokulith, Kodak T-Max dev, Ilford Multigrade and Tetenal Dokumol good!

    Tetenal Dokulith is well balanced and has a nice touch of 'grit'. The first 3 are all quite similar with Multigrade being a bit grainer.

    I also like Dokumol for the grain and graphicness.

    The D19/67 processed films are all push processed. Not so keen on them but useful to see.

    I want to try the Tetenal Dokulith. It reminds me of the first time I dev'd Tri-X Super 8 with a Tetenal Reversal kit. Exciting.

    A very useful page, thank-you.

    [Edit - I think Tetenal Dokulith is long gone]
     
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  15. mr.datsun

    mr.datsun Subscriber

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    Thansk, Gerald. YEs that is a good one – it's the PDF that made me decide to try PQ, using their suggested timings and dilution. I'm going to add the sodium thiosulphate next.
     
  16. Tofek

    Tofek Member

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    If you look at the page "educate" you'll see he advises 6 min of first development with Dokumol 1+9 or Dokulith 1+3. Anyway, the development times used for the test are the same for all the developers, that's what matters. And in the introduction of the section he mentions the use of Tri-X in all b&w tests.
    As for Dokulith, I've been looking for this one too. I had one Orwo UN54 film processed by Frank of this lab, he told me he used Dokulith, and the result is stunning : bright film and nice contrast. When I asked him he advised to look for Dokumol as a replacement.
     
  17. Photo Engineer

    Photo Engineer Subscriber

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    1 liter of 10% Hypo is 100 g/l and added to D76 will result in 50g/l of Hypo and 1/2 of the rest of the D76 ingredients just by dilution alone. This will ruin the developer. If you substitute DTOD with Hypo, you would use about 1 - 2 g/l of Hypo in the D76. But then, look at the other developer. It has Bromide in it as a restrainer which changes the action on the film totally.

    So, they are not interchangeable nor are the amounts of hypo useful - unless you want a monobath. Hah!

    BTW, look at the HQ amounts in the two developers. That should give you some hint that something is different!

    PE
     
  18. mrred

    mrred Subscriber

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    I use dektol and in my experiance it has performed the best. You need a strong developer to build up the contrast and I don't think D76 will achieve the best results, although it will work.

    Different films will require different levels of solvent. I use a "hypo" solution that I add to the developer just as I use it, in a one-shot metheod. I documented what I did here... http://myfilmstuff.blogspot.ca/2011/04/my-bw-reversal-process.html .
     
  19. mr.datsun

    mr.datsun Subscriber

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    Tofek. Sorry - i didn't get round to reading further than the test pages for the details before making the wrong conclusion. Dokumol is worth trying as a replacement for the Dokulith and I'll be tempted to try when I finish testing with the PQ. But I also thought that the TMAX dev and the Multigrade looked quite similar to the Dokulith – at least from the samples.

    I suppose we should find the formula for Dokumol to check which type of bleach it is compatible with, if we're going to try it.
     
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  20. mr.datsun

    mr.datsun Subscriber

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    mrred. It seems that D76 is out for me. I've heard of people using Dektol. Nice to see you documenting and sharing your method on your blog. Have you got any samples?

    Dektol uses sodium sulfite so I guess should be fine with a permanganate bleach.
     
  21. mrred

    mrred Subscriber

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    I use Dektol because it is the strongest and does not require additives to get the job done. Excepting a little hypo.

    Some samples can be found at http://www.flickr.com/photos/peterbcarter/sets/72157629496128586/ . This was a test to compare ORWO UN54 with Foma 100. Foma 100 does not require any hypo and is just about the perfect starter reversal film. All the shots in my gallery (at this moment) are reversals.

    Note that scans do not do reversals much justice. Projected, or at least through a viewer is my prefered way to view them. In my opinion it is the most perfect way to shoot film. You cannot get any greater detail. However the scans are still higher quality than negitive scans.

    The shot of the train station deck was done on my last roll of Neopan 400 120. It is a truly beutiful 6x9 reversal. I had printed 13x19 and hung on my wall. It can go much bigger.

    One does not have anything to do with the other. They are seperate steps.
     
  22. Photo Engineer

    Photo Engineer Subscriber

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    Dektol is a paper developer which has no concern for image quality. D75 and other film developers are designed for film quality Oh dear, I guess you younger guys do not distinguish between film and paper developers.

    PE
     
  23. mr.datsun

    mr.datsun Subscriber

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    Photo Engineer. Thank-you for your previous comment about D94a. You confirmed the growing opinion that D76 would make no substitute for D94a despite a claim I read elsewhere that said it could.

    With regards Dektol and the use of paper developers for film reversal developing amongst the younger generation. Look at The Darkroom Cookbook and the 2003 Ilford Application Sheet on reversal processing.

    The Darkroom Cookbook which was first published in 1994 by Focal, so not exactly a baby on the subject. In the section on reversal processing in the 3rd ed. it states that 'The first stage is known as primary development. In this stage, the exposed film is developed using an energetic developer to ensure that every exposed grain in the emulsion is developed.'. An energetic developer. I believe that paper developers fit that bill.

    Then in the 2003 Ilford Application Sheet on Reversal Processing it suggests using either Ilford Bromophen 1+1 or Ilford PQ Universal at 1+5. Ilford Bromophen is a paper developer and Ilford PQ Universal is a paper and film developer.

    Also, the first time I reverse processed Super 8 Tri-X was in the 80s. The Tetenal Kit I used specified the use of paper developer.

    If you have used other (film) developers for b&w reversal processing (especially Tri-X), I'd love to hear about them and how they worked out!
     
  24. mr.datsun

    mr.datsun Subscriber

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    Thank-you for showing us the scans. They look fantastic even in that form. I'd be happy to get a bit of that quality in a Super 8 reversal film which is where I'm heading with my experiments on 35mm.

    If your dev uses Sodium thiocyanate, then you should not use a permanganate based bleach. They are not compatible* and this has been discussed elsewhere (possibly on this forum). It is also mentioned in the Kodak 2000 document 'Processing KODAK Motion Picture Films, Module 15 Processing Black-and-White Films'. Bleach R-10 (Potassium permanganate) should not be used with developer D94 (which has Sodium thiocyanate). D94a type dev (which is safe with permanganate) uses DTOD instead of the thiocyanate. See section 15-25 and 15-26 of the document. I know in theory that after washing there is no developer left on the film but not mixing the two substances in the reversal process is the recommendation.

    I do not want to use a dichromate based bleach (and it is not even available in the UK) therefore I need to think about what is in the dev. The use or non-use of the dichromate has already caused enough heated debate, so let's not pursue that one, please.

    *I have read a description of the chemical reaction between the two but cannot find it at this moment.
     
  25. mr.datsun

    mr.datsun Subscriber

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  26. mrred

    mrred Subscriber

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    I stand corrected on the bleach. Opps.

    I used a batch of D19. At the time it was besting other developers, but it seemed to favour TMY or TMX and not the films I was using. I had perfect results from dektol (contrary to Mr PE's opinion). As a bonus, it is a fraction of the cost.

    It should give you exactly the same look as the Super-8 reversals. It is the same process.