sodium thiosulfate and b/w resersal question

Discussion in 'B&W: Film, Paper, Chemistry' started by NDP_2010, May 5, 2012.

  1. NDP_2010

    NDP_2010 Member

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    Hi,
    I was reading the ilford reversal process and it said to add sodium thiosulfate (8-12g/L) to the first developer. I was wondering if this step was necessary, and why (i thought sodiu thiosulfate was also used as a fixer?), and if this step isnt used what is the consequence.

    thanks.
     
  2. jnanian

    jnanian Advertiser

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    hi

    i am not sure what the reversal process is ..
    but sometimes the first developer is converted to a monobath
    by adding fixer ( hypo - sodium thio ) to it. this can weaken
    and slow down the development process ...

    i am in the middle of learning the quirks of a tintype process
    where it is similar, there is a fixer in the developer, AND some sort of bleaching agent ...
    lots of fun :smile:

    good luck !
    john
     
  3. Nicholas Lindan

    Nicholas Lindan Advertiser

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    It will work w/o the thiosulfate - it's only really needed if you are making slides for projection. I use reversal processing for enlarged negatives for new cyanotype with lith film and don't bother with it.

    The addition of thiosulfate gives clearer highlights(slide)/shadows(enlarged negatives). It removes undeveloped silver. The greatest relative reduction is where there is the most development [the parts that go black in the first development] and the least undeveloped silver. This undeveloped silver then gets developed in the second developer.
     
  4. Rudeofus

    Rudeofus Subscriber

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    John, the B&W reversal process creates B&W slides from clear based B&W film just like E6 process creates color slides from E6 film stock.

    About the fixer component in B&W reversal: This appears to be a common pattern in reversal processes, E6 uses thiocyanate, Ilfochrome uses thiosulfate, B&W uses either thiosulfate or thiocyanate.

    This page attempts an explanation why the extra silver solvent must be in the first dev.

    In case you try this with a permanganate based bleach: By all means make sure the permanganate is completely dissolved before use, however long it takes. I was careless once and got nasty uncorrectable spots on my B&W slides!
     
  5. jnanian

    jnanian Advertiser

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    hi rudeofus -

    thanks for the explanation and links :smile:

    the more i think i know about photography,
    the more i realize i have less than a clue about photography !
    ... and even after doing it for another 38 years, i will be just as clueless :smile:

    the tintype process i mentioned is the rockland's silver gelatin tintypes .. and it uses both thiosulfate AND thiocyanate in the developer
    and then a regular fix bath afterwards ...

    chemical photography certainly is a form of alchemy ... base materials ( clear plastic base, tin/aluminum, paper ) and magic potions

    (looking for my conical hot with stars and moons)
    john
     
  6. hrst

    hrst Member

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    I found out that the amount Ilford suggested was WAY too much for some films; at least Agfa APX100 I tested. 8-12 g/l is probably tested for some Ilford films. Better to have too little than too much. I would start at 1 g/l and go up if unsatisfied with hilights in real-world photography.

    The idea is, as said, to clear the highlight fog by dissolving (just like fixer does) halides - it takes smallest grains first; those small grains that probably didn't get enough exposure to render them developable.

    So as you can see, it really works like fixer, competing with developer. At the suitable level, it fixes the image away "just a bit" to lighten it up. So, the level is critical and depends heavily on film. If you have too much, it works too quickly and fixes most of the image away during the development. You can leave it out but then you will have somewhat muddy, foggy highlights no matter what.
     
  7. Oxleyroad

    Oxleyroad Subscriber

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    I could not have said it better.

    From my own work, I started with the Ilford recommendations and progressively reduced the amount of hypo. For the most part I don't use any hypo at all now. I process predominately 16mm cine (Fomapan R100 and ORWO UN54) and to a lesser extent all the other formats 35mm 120 and sheet. I have processed Foma, Ilford, Kodak, Efke, Shanghai and ORWO. Each having their own peculiar behaviour to the reversal process and the results have been excellent for projection.

    What I have found is when using permanganate bleach the emulsion is REALLY softened and easily damaged. I switched to dichromate bleaching and have yet to damage a film.
     
  8. NDP_2010

    NDP_2010 Member

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    very good info here thanks everyone.

    oxley, where do you obtain the hypo in australia? Also can you give more details on the dichromate bleach, is it still used with sulfuric acid? what concentrations (and also where do you purchase it?)

    thanks.
     
  9. mrred

    mrred Subscriber

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    The devloper (what ever chosen) devlops enough silver to give the required contrast. The hypo is *required* to remove the excess silver to allow the highlights to be highlights. Like everything in life, it's a balence.

    Think of it like this..... You are hollowing out a 2x4 with a 3d shape of a human. It does not go all the way through the wood. The hypo is the equivelent of plaining off the excess wood until the bottom of your carving is on the other side. So now the depth of you carving is the depth of the wood. If you have a high depth of a carving, not much plaining is required.


    So....

    You use a strong enough developer to get as much contrast as required. You then use enough hypo to brighten the immage to look correct. To say you never need hypo is as just as incorrect as saying you always need it. It will always depend on the film you are using.

    What I do is desolve 16g of hypo in 250 ml of distilled water. I then add amounts to the developer I put in the can. This makes work with any film I want to use and not to have a "special developer" version for each one.

    I keep my most recient notes over here... http://myfilmstuff.blogspot.ca/2011/04/my-bw-reversal-process.html
     
  10. hrst

    hrst Member

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    Yes I agree, it's about balancing. But even without any hypo, you will always get an image!

    When I started with the Ilford recommendation, I got completely blank film with nothing in it! The high amount of hypo fixed the image completely away, which I found a little bit surprising. Maybe APX100 was so different from Ilford films. Anyway, it took a few attempts to understand what was going on as it was my first attempt on reversal processing and when I got nothing, I was first suspicious about bleach, clearing bath and 2nd developer.

    Of course, I could have noticed that the film looked too clear after 1st dev, while it should look like unprocessed ("milky") film with black negative image superimposed, like a paper.

    So practically, the 1st developer was working like a negative developing monobath.
     
  11. mrred

    mrred Subscriber

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    If you tried ACROS 100 you would have gotten a strip of black. The properties of the film have everything to do with it. I guess how fast or slow a film fixes is an indecator for how much hypo to use.

    I always do a quick inspection after the bleach. It's nice to know early when I have screwed up.

    I tend to do strips initally, exposing -5 to +5 in 1 stop increments - with a grey card and cards in the shot stateing what exposure it is. I start off with no hypo and go from there. It's a pretty fast way to ball park.
     
  12. Mike Wilde

    Mike Wilde Member

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    I know I am late to this thread, but every first developer formula I have seen used thiocyanate, not thiosulfate.

    The thiocyanate makes sure everything that iis on the verge of being developed gets developed is the way I understand it.

    That means that the clear areas of the final product transparency are as clear as they can be, rather than being dim with residual fog.

    I am most willing to be corrected on this, however. I am working on memory, and not my reversal processing notes to make these comments.
     
  13. Rudeofus

    Rudeofus Subscriber

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    Mike, I linked to one recipe for B&W reversal with thiosulfate and one with thiocyanate. I have no idea which one is better or whether there is a difference at all.
     
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  15. holmburgers

    holmburgers Member

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    According to E.J. Wall and also Grant Haist, potassium thiocyanate is the preferred solvent at 0.2% according to Wall/Jordan and at 0.5% according to Haist. Above 5g/L and density goes down, below 5g/L and ISO drops and you get longer development times.

    Contrary to popular formulas, hypo is not considered to be very good, resulting in lost shadow density.

    Never tried it myself, but that's what "the big dogs" say. Here's a bit more on this post.

    Agreed that Ilford's recommendation is way too high.
     
  16. hrst

    hrst Member

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    Hypo seems to be VERY popular in formulas published on the internet. Maybe because Ilford recommends it. Or because it's more readily available; many already have it for fixer or farmer's reducer.

    I used hypo in reversal RA-4 first developer with good results at low levels. I don't remember if I tested thiocyanate or not, at least I planned to! I used thiocyanate on experimental Ilfochrome developer. It seemed to brighten shadows more than highlights. For digitally oriented people, I would say just like gamma correction tool.

    Both can be used for the same purpose, but probably with a little bit different kind of results. It's HEAVILY dependent on film but also heavily a matter of taste. The only way to know is to test.

    For example, do test strips with no hypo - 0.25 g/l - 0.5 g/l - 1 g/l - 2 g/l - 4 g/l and same with KSCN. Bracket exposures for every test strip widely enough, because the "optimum" exposure may also vary depending on the formula.

    Anyhow, it's easiest to start with the basic formula with no halide solvent at all and then introduce it to see the effect.

    And, tinkering with the formula is not by any means limited to just halide solvent. Maybe to keep it simple, I would take the development time as a parameter, too.

    Then there is SLIMT......

    You could dedicate your whole life to just one reversal process if you wanted to. Or you can just pick a formula to get some results you will probably like.
     
  17. spatz

    spatz Member

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    All the ingredients can be bought from vanbar in sydney (the dont stock it - it comes from vanbar in melbourne and takes around a week to get to sydney) except for the sulfuric acid. i replaced it with sodium bisulfate which you can buy by the kilo from pool stores which is sold as a pH reducer. for the 1 litre bleach i use around 60g of sodium bisulfate. i havent tried it but you can buy a product called mo-flo (blackwoods stock it as a drain cleaner) which i believe is around 40% sulfuric acid which you can water down to the right concentration.
     
  18. Gerald C Koch

    Gerald C Koch Member

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    Typically thiosulfate is used at twice the concentration recommended for thiocynate. They are used to cleanup the hightlights when making BW slides. The usual concentration is 2 to 4 grams of thiosulfate per liter of first developer.
     
  19. NDP_2010

    NDP_2010 Member

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    would it be possible to use a small amount of fixer (i have rapid fixer) instead of the thiosulfate?
     
  20. Oxleyroad

    Oxleyroad Subscriber

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    I buy from Vanbar as spatz said was possible in earlier post. The sulphuric acid I was given 4 litres of conc about 10 years ago from an old roofing plumber and it has kept me and others going for a while.

    The Bleach I use is Kodak Bleach R9; and the soup as follows
    Water - 1litre
    Potassium dichromate - 9.5g
    Sulfuric acid (concentrate ~98%+) 12ml
    Adding the acid real carefully and gradual to the solution.
     
  21. Gerald C Koch

    Gerald C Koch Member

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    NO, fixer contains other chemicals other than thiosulfate which could have undesirable effects on the developer. Even plain ammonium thiosulfate cannot be used. You have to use sodium thiosulfate or sodium/potassium thiocyanate.
     
  22. NDP_2010

    NDP_2010 Member

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    thankyou.
     
  23. dr5chrome

    dr5chrome Member

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    sodium thiosulfate or sodium/potassium thiocyanate

    Reversal B&W process is like any other photographic process - it's what you make of it. Haist had his formula for it 30+ years ago, good maybe for the films of the day - but not optimal. Some recipes produce very good result, some very poor.

    The B&W reversal process for today's films is much different than yesterdays. Though there are basics, small details matter for the best outcome. sodium thiosulfate or sodium/potassium thiocyanate rob an emulsion of it's potential if it is used in a reversal B&W process. It is best to alter procedure or other baths to off-set the use of these agents. The image result is much more desirable.

    regards, dw
     
  24. DarkroomExperimente

    DarkroomExperimente Member

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    I was wondering...if adding a normal fixer ( like ilford rapid fixer, etc ) directly to the developer is a bad idea...what about running the film through a dilute fixer briefly after 1st development?
     
  25. Gerald C Koch

    Gerald C Koch Member

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    NO again. However you can use dilute Farmer's reducer to clean up the highlights bit it is tricky to do this.
     
  26. Steve Roberts

    Steve Roberts Member

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    I thought I'd cracked it at my second attempt, developing in Rodinal with no thiosulphate or thiocyanate. However, my third roll was a big disappointment, with a general muddy appearance that seemed to indicate that I needed something in that first developer. I've bought thiosulphate, but have yet to try it.

    Steve