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  1. #1

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    C41 questions about times, what each part does and cross-contamination

    Hi all,

    I recently started developing color at home. I heard about how much harder it supposedly was than B/W and was a little anxious to start that whole chapter. My first roll turned out fine, which made me sigh in relief; too bad I've had very mixed results since then. This might have had something to do with the different kinds of shoddy films used, but still.

    Anyway, I'd like to get a better understanding of the C41 chemical process. I'm using the C41 digibase kit (5 liter, from Maco); this kit doesn't have blix, but seperate bleach and fix. The technical data sheet can be found here.

    My last couple rolls turned out a little milky/brown and upon reading the sheet it looks like my bleach/fix is starting to lose its strengt. Fair enough (even though they were supposed to last a couple rolls more). It might be worth adding that they only look milky/brown when looking from the emulsion side. When I look through the base of the film, they just seem a little dark.
    After troubleshooting I went back and re-bleached and re-fixed a couple of rolls to see what this would do. It didn't seem to help much. Would this even ever do anything after stabilizing? (so bleach->fix->stabalize->bleach->fix->stabalize is what I did). I've also heard of people using a B/W stop-bath in between developing and bleaching.

    This also made me think of cross-contamination and it made me realize I don't know much about what every chemical component does in the C41 process.

    Develop: this is pretty self explanatory I think.
    Bleach: No clue
    Fix: the same as with B/W?
    Stabalize: Stabalizing of the colors and wetting agent (is what I read in another thread).

    What can spoil what and how fast?


    Lastly, and for me most importantly, is getting a better understanding of how strict the times used in the technical sheet are. The developing part is of course very time-dependent (just like with B/W) and the times used here are very important. But what about bleaching, fixing and stabalizing? With B/W I tend to use a stop-bath from 1-5 minutes and I'll fix anywhere from 4-10 minutes; mostly because I'm always running around doing other things in the meantime. I've never had any problems with this because 'over-stopbathing' and 'overfixing' don't happen, unless you're really pushing it.
    What about overbleaching, overfixing and overstabalizing with C41 chems? Is that even a thing. I don't like being anal about every little step and rather take it easy. I accidentaly bleached my film for 6 mins instead of 4 and it didn't really seem to matter in the results.

    Any answer is appreciated. Thanks!

  2. #2
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    Both bleaching and fixing have a minimum time but no max really short of damaging the film due to mechanical or temperature stress. Same with washes.

    Fixing is the same as B&W. Bleaching turns the silver into a form that can be removed by the fix.

    The developer and fix can spoil just like their B&W counterparts, and all solutions have a maximum capacity.

    Rebleaching and fixing works in most cases, unless the solutions are exhausted or if the fix has gone bad.

    PE

  3. #3

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    Processing C41 colour is quite easy providing you can keep the temperatures within .5 of a degree. You seem to have managed this with your 1st roll, so far so good. Processing times for any film is 3 mins 15 seconds, so there is no need to worry on that score.

    After the deveopment stage as you have done the bleach stage comes next for a minimum of 6 minutes at 38 degrees C (I do it for 7) The bleach stage is necessary to remove all the remaining colour dyes.

    It will not be included in your instructions but I also give the film one extra water rinse between bleach and fix the film in clean water again at 38C.

    The fix stage, as you rightly state is the same as processing B&W and makes the image permenant. Again it needs at least 6 mins, it won't hurt to do it longer. Within reason extended bleach and fix will do no harm but don't over do it. Stabiliser the same. You can use a stop bath between the development stage and the bleach, but again don't over do it. 30 seconds is enough!

    The milky brown colour of your later films suggests to me that they have been under bleached and under fixed. 6 mins is the standard of all kits I have used in 25 years. The success of your 1st film may be down to the fact that the bleach was fresh and worked quicker than the later film which was in partially used chemicals. This is probably the case in your subsequent films too. Cross contamination, I don't think is the problem. It will take a lot of different chemical mix to produce cross contamination in the bleach amd fix stages. The development stage will produce poor results if the chemicals are contaminated. (Under development, false colours are two)

    I am currently using a Fuji Kit and I expect to get about 8-10 36 exp films bleached and fixed out of half a litre of each bath. For the the developer, I mix enough for the number of films to be processed, use once and throw away. When the bleach and fix baths are nearing exhaustion, they will start to smell of Hydrogen Sulphide (Bad eggs). Unused or with little use, Bleach and Fix baths will last a reasonable time. (at least 3 months) The developer will go 'off' within a few days which is why I mix only enough for the films to be developed and throw it away afterwards. This also cuts down the risk of cross contamination.

    If you get the bleach and fix stages in the wrong order there is no way the film can be recovered.

    As colour dyes will fade over time the stabilising bath will slow this down and keep the colours true for longer. A stabilising bath means you don't need to use a final rinse with wetting agent.

    Don't give up, you will get there.
    Last edited by BMbikerider; 05-01-2015 at 05:49 PM. Click to view previous post history.

  4. #4

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    Wow! Great answers. Thanks a lot!
    After I left them to dry for 90 minutes I went and checked how they were looking. The milkyness faded quite a bit. They're still not a hundred percent clear, but almost there. Instead there are a TON of little drying marks. Marks I'm familiar with are more like smudges and not that noticeable, but these are just tons and tons of white little specks (which show up on the quick scans I just made with my Pakon scanner). The couple rolls I did earlier today didn't have this problem. The only thing I did different that first time is that I did a quick rinse with a wetting agent after the stabalizing step, which makes me believe the stabalizer isn't doing its job right as also acting as a wetting agent. Should/could I throw in some wetting agent into the stabalizer?
    Here is a picture of what it looks like. I've had this problem before (but not to this extent), which is why I washed with a wetting agent this time to see if this avoided the problem (and it did). Does washing after the stabalizing step compromise the archival qualities of the film (eg. fading colors)?

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    Washing after stabilizer affects dye stability. Stabilizer or final rinse should always be the final step in a color process. Your film has a lot of grunge on it. Something is in the solutions or water supply. And, the process looks seriously off.

    PE

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    Rinsing in wetting agent after stabilising should not make any difference to the stabiliser. Basically, most stabilsers use formadehyde and once that is on the film, it takes a lot to remove.

    On the other hand I have colour negatives which are over 20 years old and show no signs of deterioration and will still print OK, so the stabiliser is fine but I would suggest isn't strictly necessary.

    Judging by the colour of the film base layer it is too drk and the wrong colour. It should be a more orange colour and clearer. Again pointing to under bleaching and under fixing.

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    Under bleaching, under fixing --- or fog!

    PE

  8. #8

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    Thanks for the help!
    I've learned a ton arleady.

    Here's a closer look at the spots:


    The weird thing is, they're ONLY on the base side. The emulsion side is totally clear. It's some kind of gunk, which wipes off pretty easily, but still: it shouldn't be there and I can't figure out where it comes from. Especially because I'm using a liquid dev/bleach/fix/stabalizer. I've only seen stuff like that with powder chemicals (only a couple of times). It's not there when I hang the film to dry. It seems to have something to do with the fact that the wetting agent isn't doing its job right. There's a trail of little droplets of liquid that don't slide down the negative. When they evaporate, the result is a litte spot.
    Here's a negative against a white background.

    As you can see it looks good (to my eye). The base is clear and orangy. The scans turned out really good too.

    I've got another question. Before I bleached for 4 mins (per the instructions) and fixed for 6. I made a new batch of both bleach and fix and did both for 6 minutes on my last roll. When I take the negs out of the stabalizer, they emulsion side is very milky and translucent (when looking through the base, it's just a little darkish). When they dry, they look just fine (like in the picture above). Is this normal?

  9. #9
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    Did you use tap water and is it hard, to do the solutions? Or more specifically the stabilizer? I had a similar thing when developed c-41 for the first time, I used tap water when did the stabilizer solution and do to the water here being very hard, it creates a white foam residue in the film.
    The digibase kit instructions alert to use distilled water for the final solution and also asked here for advice at the time.

  10. #10

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    Quote Originally Posted by Rhodes View Post
    Did you use tap water and is it hard, to do the solutions? Or more specifically the stabilizer? I had a similar thing when developed c-41 for the first time, I used tap water when did the stabilizer solution and do to the water here being very hard, it creates a white foam residue in the film.
    The digibase kit instructions alert to use distilled water for the final solution and also asked here for advice at the time.
    I looked right over it! Thanks. That must be the problem. I'll go make a new solution with distilled water!

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