C41 Chemistry

Discussion in 'Film and Processing' started by bob_bell|2, Nov 15, 2013.

  1. I have three boxes of sealed C41 Chemicals, each contains 3 sealed bottles: Part A Color developer, Part B Color Developer and Bleach Fix. (mine say "colour" because I am in England).
    They are well past their "best before" dates but are completely sealed (plastic/foil seals on each bottle that are part of the plastic bottle and have to be punctured to get at the liquid).
    My question is what color should they be?
    The Dev A has a purple color to it.
    The Dev B is clear.
    The Bleach Fix is brown.
    It has been a few years since I did any C41 processing so any hints about how to check if the chemicals are OK would be welcome.
    Also, what happens if you mix 100 ASA C41 film and 400 ASA film in the same tank? The Developing times are the same but the Bleach Fix times are 50% longer for 400 ASA. For example, what would be the consequence of using the longer bleach fix on 100 ASA?
    I'm not a novice at processing but all my activity has been E6 transparencies or digital, not C41.
    Any advice on how to spot dead or depleted chemistry will be most welcome!
    Thanks
    Bob
     
  2. C-41 is a standard process. All films have the same processing time, including Bleach/Fix, regardless of film speed. Much simpler than traditional black and white.
    The only way to determine dead chemistry is to run a film through it. That's why labs have test strips. We commoners just use a length of film with non-important shots to check. I have lost 'important' films to dead developer. It is is distressing.
     
  3. Thanks Bill.
    The instructions with the C41 clearly give two sets of bleach fix times - one for 400ASA and over and one for 200 ASA and below. I thought it should be standard.
    I will run a test strip as you suggest but would still like to know what the chemicals should look like as this might save a test strip. Easy in a contiuous proesses lab, but a bit tedious if you use a rotary processor.
    Thanks
    Bob
     
  4. As the other poster said the bleach-fix times would be the same in the standard process, but that is the least of your problems.
    Proper C-41 developer should come in three parts instead of two. Even if it was new I would not trust such a developer to give proper results. I am not familiar with this developer but the purple you mentioned does not sound good at all.
    The proper C-41 process uses a separate bleach and fix. When combined, bleach and fix interact with each other and have a short life, especially with C-41, as the concentrations of each needed to do their job properly on film must be high. With paper, the concentrations needed are lower so a bleach-fix works well for paper. If the bleach-fix comes pre-mixed, the concentrations must be low to have any shelf life at all so it would not do as good a job bleaching and fixing as a separate bleach and fix, and would still have fairly short life. Your negatives would likely have retained silver and would likely fade prematurely, if it works at all.
    Definitely run a test strip before using it on anything important!
     
  5. C41 is a proprietary process by Kodak and Fujifilm. A standard C41 developer has 3 bottles of chemicals marked as part A, part B and part C. Then there is a bleach and a fix. At the end of processing then there is a stabilizer to be applied.
    The only chemical in the C41 process that will go bad within a year or two after you get it from a store is the part C of the developer. Everything else will last many many more years with no worries. Part C is usually in a glass bottle tightly capped (but not sealed). Once its cap is unscrewed and opened it will go bad within 6 months or so. It will last about two years unopened. If the liquid has turned brown or black it has gone bad.

    If the C41 kit you have has a developer that comes only in part A and B, and you have a blix. It tells that it is not a standard C41 kit. If your developer part A and B look clear, not brown, I think it is likely still good to use. My question would be if it will produce the right colors and if the colors will fade by using a 3rd party non standard C41 process. You did not mention a stabilizer. It is important to apply stabilizer or the colors will fade in a couple of weeks. The newest term Kodak uses is called Final Rinse. It does a similar thing as a stabilizer did before.
     
  6. The dyes used in modern films are very stable and will not fade if the Final Rinse is not used after proper processing, and the films are stored properly. Rather, the Final Rinse is necessary to prevent fungal growth in the emulsions. I have several rolls I developed myself several years ago without the Final Rinse step and there has been no fading. But it should be used if you don't want things growing on your films down the stretch. The Stabilizer that preceded the Final Rinse (introduced sometime in the last 10-15 years) was necessary to prevent fading of older films. Any extant Stabilizer can be used on today's films but Final Rinse should not be used on older films.
     
  7. The process is not standard C41 but a two bath process based on different chemistry.
    I usd it for around 15 years (and my negatives are fine and have not faded.
    About 8 years ago I stopped using film and doing my own processing of colour negative film. I work with colour transparencies or digital. Now that scanners are excellent I want to do a few color neg films plus some photochromic black and white that uses C41 chemistry.
    I have three completely sealed kits of this two bath chemistry and just wanted to know what colour the solutions should be when opened.
    If, for example, the Part A colour developer should have a faint purple colour then it is worth my while doing a test run. But if it should not, then I won't bother.
    A lot of companies produced their own two bath C41 chemistry and the products had excellent shelf life. Unfortunatly Paterson/Photax who market this kit don'tr seem to be around any more.
    But thanks for the advice - it looks like I have to do a test strip.
    By the way, I have never had any of my transparencies or negs fade. That includes my duplicates on proper Ektachrome dupe film. The same is not true of some commercial transparencies I purchased (also on dupe film) that have faded very badly despite identical proper storage.
    I am now resigned to doing a test strip. being an amaterur, the processing is only a small part of the rigmarole of getting the proecssor set up and the temperatures stabilised.
    A really big "Thank you" to everyone who has contributed.
     
  8. Are you familiar any sensitometric tests done on this process? That is, with a control strip or gray scale and a densitometer? C-41 is a very exacting and sensitive process and it is very unlikely that a non-standard process would produce negatives with no crossover or other problems. They may look fine to you, but a side-by-side comparison with properly processed negatives and their prints may show otherwise. I know this from working with C-41 chemistry and even mixing my own from formulas. But if the results are acceptable to you, that's what counts.
     
  9. There is nothing strange or wierd about two bath colour neg chemistry or that the film developer is just in two parts and not three.
    Yes, I did not only full H&D desitometry tests but also chromaticity tests based on known calibrated colour samples under known calibrated illuminants
    It was fine - absolutely fine. But this was a long time ago. It was better than the Kodak reference (H&D curve) with cleaner whites and blacks and better saturation.
    My background is that when I was the Chief Engineer of the worlds largest lighting solutions company, I became an expert on photographing lighting installations. because this was our business. Getting a realistic photo with the correct colour rendering of objects the light source was essential. I am not talking about just getting a white balance - anyone can do that, but pictures that accurately captured the colour rending properties of the light source.
    The gamut area of colour transparency film is larger than colour negative. Plus negs are a two part process (film + print) with two stages where colour fidelity is degraded. Stricty speaking transparencies are a two part colour process (the spectral sensititivity of the emulsion and the spectral transmittance of the dye do not match) and negatives are a four part colour process (two lots of sensitivity curves and two lots of dye colours). Also the H&D curve is greater (0.2 to 3.2 vs 0.4 to 2.4 for Neg with the colour layers' H&D being congruent but not on neg).
    I dfd extensive trials of every light source. I used matched booths with a full range of calibrated colours (plus Ra8 colour samples) and a human mannequin that had been specailly painted to exctly match the spectral reflectance of "standard" human skin (and texture). One booth was a reference so each exposure had the test plus the reference.
    There is, of course, a huge difference between taking photographs that only have to look good and taking photographs that technically reproduce (so far as is possible) the true effect of "white" light with colour rendering indices that vary (such as standard fluorescent).
    So, yes, I did a lot of work on the use of colour film with far more detailed desnsitometry and colorimetry than used in a processing lab. At its best it was an inferior process to transparency (check Kodak's own data)
    Although I shunned colour negs, the processing chemistry that I used for them produced excellent colour negs with a good H&D range (far better than mini-labs).
    The chemistry was excellent (now owned by Fuji) and it produced A1 results.
    But none of this has anything to do with the price of fish. That was not the subject of my query. I don't do much colour neg photography and just fancied doing some for a change but it was so long ago that I cannot recall the colour of the fresh unmixed chemicals. That's all I was asking.
    When I get round to it, I will run a test.
    Thanks
    Bob
     
  10. The use of a two part developer IS a bit strange, since manufacturers almost always use three parts.

    I am quite surprised that your process gave the results you say, especially the blix. Processes sold that use a blix almost always results in retained silver. That is why Kodak, Fuji, and Agfa never marketed a blix but always a separate bleach and fix. I am surprise your process is not marketed anymore if it was that good. I don't think Fuji sells it.

    Color negatives are masked; that is the reason for the uniform orange color on them. The purpose is to eliminate dye impurities. Therefore a printed color negative essentially has only one step of degradation, the print, which cannot be masked. Slides themselves are not masked and therefore have some degree of dye impurities present; similar to a print from a color negative. Now, if you print a slide, the print will be inferior to a print from a color negative due to the lack of masking. Also, negatives have lower contrast than slides and can therefore record a greater dynamic range than a slide. Prints from slides will therefore often have blown highlights due to the high contrast of the slide (compared to a negative). The print material range cannot handle such high contrast. It is true, however, that a projected slide or one viewed directly will have greater dynamic range than a print. Color correction due to masking, and greater dynamic range is the reason Hollywood originally chose color negative film rather than reversal film to shoot movies on and then make release prints.
     
  11. I am using the Tetenal C41 kit for the first time but the instructions do not mention agitation. Should it be every 30 seconds or every minute and do I turn the tank up side down as I do for B&W?
    Also it recommends pre-heating the tank but should the film be pre-washed also or is there any need to do this?
     

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