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  1. #1
    JLP
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    Obsidian Aqua problems

    Posted this question on the Large Format Forum but have feeling that a few photographers here also use this developer.

    After reading a bit about this developer I became interested in trying it out and after checking what I had of chemistry in stock I decided to give it a go.
    I mixed up 250ml of part A as I had enough Catechol for that.
    I first tried with Sodium Carbonate for part A but could have used Pot Carbonate as I had both.

    The problem I have are extremely thin negatives, I have developed Pan-F and TMY both in 120 format and I can't get anywhere near box speed as I read should be possible with reduced agitation.
    With TMY I get no more than Iso 100

    Today I mixed up a new B solution from Pot. Carbonate but it did not change a thing.

    Is it possible that my Catechol was to old? it was stored for a few years, maybe 4 but still looked normal or I should say looked like it did when I purchased it.

    I used Pyrocat MC for a few years so I know what the negatives should look like but with OA there's just no similarity.
    Any idea what could be the problem?
    Thanks.
    _______________
    Jan Pedersen
    http://janlpedersen.com

  2. #2
    MDR
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    Dear Jan,

    I've been a longtime user of Jay's Hypercat developer never tried OA though, and was wondering how long you've developed the film. Jay advices 12 - 15 mins as starting points and 10sec agitation every 3 mins. The catechol if kept dry and in a dark container should keep. Part A has no carbonates in it, it's either sodium or potassium metabisulfite. Part B the carbonate solution is either a 0.666% solution of potassium carbonate or a 0.5% solution of sodium carbonate so the choice of carbonate does play a role. Pyrocat negs btw do not look exactly like Hypercat negs or I belive OA negs try to print the negs as the look of Pyro negs can be very deceiving.

    Hope you have better luck next time

    Dominik

  3. #3
    Rick A's Avatar
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    While I haven't tried OA, I do use pyro developers. My experience with them is they all tend to look "thin" but that is misleading, as they all print fairly easily, no loss of detail. I tend to develope 10-15% longer than starting times listed, and get somewhat contrasty negatives which I prefer for my style.
    Rick A
    Argentum aevum

  4. #4
    MDR
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    Jan could you post a photograph of the neg?

  5. #5
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    Have you thought of asking Jay deFehr, the fellow who created Obsidian Aqua? I know he's on Flickr discussing this developer.

  6. #6
    JLP
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    Thank you all for you good suggestions.
    I know from using Pyrocat for about 5 years that a pyro negative looks thin but prints well and exposure time usually is longer than when using solvent developers.
    These OA negatives does however look way to thin. Not even the rebate information is clearly visible.
    Developement time for TMY400 at 200 was 12 minutes with 1 minute initial agitation and then 10 seconds every 2 minutes at 22 C.

    I have off line received some good suggestions and will try adding more of solution B to the mixture.
    I have tried with both Sodium Carbonate and Potasium Carbonate with the same super thin negatives as a result.
    _______________
    Jan Pedersen
    http://janlpedersen.com



 

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