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  1. #1

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    Extended C-41 Blix times

    Hi, now that Agfa have gone belly up, have swapped to Tetenal C-41 chems. Problem- their time for the blix is 4mins, my Jobo time is set and not reprogramable at 8mins. I realise the blix stage is supposed to go to completion, but will there be an adverse effect in doubling the recommended time? Tetenal instructions say a 50% increase is O.K. but what about a 100% increase. Anyones comments would be appreciated before I commit film to chemicals.
    Mike
    If you live forever, you'll learn everything. Living forever is the problem...

  2. #2
    Photo Engineer's Avatar
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    Mike, I cannot guess what Tetenal added to their blix to make it work well with color films. I know how hard it is to do the job right on color films with a blix. Therefore it would be useless for other than a Tetenal chemist to advise you on this. IMO anyone else would be blowing smoke at you.

    Dyes can be destroyed by oxidants, reductants, metals, and pH changes.

    You cannot overdo the Kodak or Fuji Bleach or Fix solutions unless you use very very long times. They go to completion with chemistry designed for the dyes.

    PE

  3. #3

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    Quote Originally Posted by Mike Lyons
    Hi, now that Agfa have gone belly up, have swapped to Tetenal C-41 chems. Problem- their time for the blix is 4mins, my Jobo time is set and not reprogramable at 8mins. I realise the blix stage is supposed to go to completion, but will there be an adverse effect in doubling the recommended time? Tetenal instructions say a 50% increase is O.K. but what about a 100% increase. Anyones comments would be appreciated before I commit film to chemicals.
    Mike
    I too use the Tetenal Colortec C-41 and have just had a look at the instructions. The blix times go from 4 mins for 1-4 films to 15 mins for 13-16 films. So there has to be quite a spectrum of useable times. There are also times for processing at 86 degrees F if 100 degrees F produces uneven results. At 86 degrees F minimum blix times is 6 mins and rises to 8 mins for 5-8 films. There's also a section on deviations in results. Nowhere there does it mention a problem caused by overblixing. All of this suggests to me that extending blix times to 8 mins isn't critical. Indeed it is essential if you use the same blix for a greater number of films.

    OK at worst, using the processing times for 86 degrees F the first 4 films will be overblixed to the tune of 33%( 8mins as opposedto 6 mins) but thereafter the blix will be spot-on. You're right that it says the blixing times can be increased by 50% but on the above basis the increase is only 33% so well within the extension.

    I can't say there won't be a problem at 8 mins with the first 4 films as I have never tried but based on the instructions I'd be surprised.

    As PE says contact with Tetenal or a knowledgeable user of Tetenal may be the belt and braces solution but based on the above info issued by Tetenal, I'd certainly have no worries if it were me.

    pentaxuser.

  4. #4
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    Just remember that 13 rolls for 15 mins vs 4 mins for 1 roll represents a different level of concentration of ingredients and a different change in concentration over time, so that range of times vs rolls may not be a good predictor. Using 15 mins for 1 roll might be like driving in a penny nail with a sledgehammer.

    PE

  5. #5

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    Quote Originally Posted by Photo Engineer
    Just remember that 13 rolls for 15 mins vs 4 mins for 1 roll represents a different level of concentration of ingredients and a different change in concentration over time, so that range of times vs rolls may not be a good predictor. Using 15 mins for 1 roll might be like driving in a penny nail with a sledgehammer.

    PE
    Point taken PE but in respect of Mike Lyons' concerns about over-blixing, I think my paragraph, 3rd from end and based on Tetenal's instructions, suggests that a 33% overblixing is well within Tetenal's safety margin. Of course, it's Mike's call.

    pentaxuser

  6. #6
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    Pentax;

    Sorry, I mistook that to mean all films at the same time. If it is a sequential recommendation by Tetenal, then that is right.

    PE

  7. #7

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    O.K. so by reusing a litre of chemicals I can get 24 sheets of 4x5 film with the increased times for each batch after the first (re-using the full 1 litre of chems ),but if I use smaller vols prorata ( 250ml for 6 sheets, 500ml for 12 sheets ) as single shot development, I should need to take into account the more rapid exhaustion of the chemicals, right? So doing it that way would need longer development for smaller vol, single shot, but how do I calculate that? Over to you guys- I defer to greater knowledge. Mike
    If you live forever, you'll learn everything. Living forever is the problem...

  8. #8
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    I've used the Tetenal 2-bath 5 liter kits for years with my ATL-1000, which has a non-programmable BLIX time of 10 minutes.

    No problems, works great.



 

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