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  1. #1
    holmburgers's Avatar
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    Removing Rem-Jet for ECN-II films and Kodachrome

    Hi all,

    First off let me say that I have no experience with rem-jet personally, but I've been talking with Photo Researcher (not to be confused with Photo Engineer) who is a former Kodak employee working on a home-made Kodachrome. He shared the following about removing rem-jet, which he does when he home processes Kodachrome.

    First off, rem-jet is an excellent anti-halation layer that is ideal for motion picture for a number of reasons. For one, the carbon black used as the black pigment is an excellent conductor of static electricity and thus it dissipates this better than any other AH layer. Also, since it is removed in processing (rem-jet means removable by water jet) there is no concern for scratches that might've been accumulated in camera transport; a bonus for motion picture cameras that feed hundreds of feet of film in a few minutes.

    Rem-jet is a dispersion of carbon black pigment (lamp black) in cellulose acetate phthalate.

    Historically (before 2000ish) the process for removing rem-jet in commercial processors has gone something like this.

    PRE-BATH: A short, 30 second, pre-bath (PB2). This includes about 100g/L of sodium sulfate and some amount(?) of borax, with sodium-hydroxide to reach a target pH of 9.2 (this # was given from memory and has the potential to be incorrect, but let's assume it's right). The sodium-sulfate serves a unique purpose; it prevents premature hydrolysis of the rem-jet layer, while the high alkalinity of borax/NaOH destabilizes the cellulose polymer. If the RJ hydrolized in this step, there would be danger of particles making their way to the emulsion side.

    WATER JET: A powerful water jets spray the back (and front) of the film to remove the RJ layer. The sodium-sulfate is quickly diluted and no longer restrains hydrolysis; resulting in efficient removal of the RJ layer.

    BUFF: A soft, counter-rotating buffer of mohair (for instance) physically removes any remaining RJ.

    Now, around the turn of the millenium this process changed somewhat. The pre-bath was eliminated and a buffered carbonate/bicarbonate solution at pH 10 was used to remove the majority of RJ in an initial bath. This solution is circulated and filtered to remove particulate matter which might deposit itself on new film as it enters the processor. I believe that the jet and buff steps were the same, though actually I don't think we addressed this issue (my bad!).

    So that's how it's done in a commercial, continuous operation, as is standard in motion picture labs.

    For the home processor of rem-jet films though, PR has shared his method which has worked flawlessly for him; resulting in no particulate matter on the emulsion side and minimum fuss.

    After a pre-bath like in the "historic" process (PB2), the reel containing the film is plunged vigorously and violently into a large tank of water (in the dark of course). Agitation and violence is the key here; lift the tank out of the water and plunge it fully in, repeating many times, getting as much air and turbulence involved as possible. Next, process immediately as usual; that is, you cannot let the film dry because if there is any particulate matter it must not be allowed to dry on the emulsion. After processing, a synthetic chamois soaked in stabilizer (ECN-II, C-41, etc.) is gently run along the length of the film on both sides with gentle but firm pressure. This should remove any remaining particulate matter without fear of scratching.

    So I hope this is somewhat helpful. I know there are people interested in removing the rem-jet, and then sending out for processing at C-41 labs. With this in mind, it seems that the chamois-squeegee step could be performed after the rem-jet removal with an appropriate (probably not stabilizer!) liquid and then left to dry.

    Just passing on what I've learned; comments and questions are welcome.
    If you are the big tree, we are the small axe

  2. #2
    Nicholas Lindan's Avatar
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    I have processed Kodachrome to black and white negative [though the reason I wanted to do so quite escapes me...].

    I removed the backing after processing. A few minute soak in a borax solution [a proverbial 'dash' in a 1/2 bucket of warm water] along with a few drops of dishwashing liquid get the backing off the loose uncoiled film with only a lite swirl. The dishwashing liquid keeps the washed-off 'jet from redepositing on the film. There were no particles of backing sticking to the film
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  3. #3
    holmburgers's Avatar
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    Interesting Nicholas, I would think that the alkaline developer might "entice" the rem-jet to break down during processing, but what's the pH on a typical developer; possibly it's not high enough?

    Thanks for sharing!
    If you are the big tree, we are the small axe

  4. #4
    choppastyle's Avatar
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    I've heard baking soda and water gets the stuff right off. I'm pretty much addicted to tungsten film so I see ECN-2 in my future.
    I take donations for beer and film​.

  5. #5
    Rick A's Avatar
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    I've also had great success with borax and dish detergent after processing. I also develope as B&W film.
    Rick A
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  6. #6

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    I brought up ultrasonic cleaner as a possible solution for non-rubbing rem-jet removal in a separate post. Holmburgers' post encouraged me to do some experiment tonight.

    [1] Cut a MP film snip and put it into a stainless tank.
    [2] Fill tank with pre-wash and let the film soak for 2 mins, no agitation at all.
    [3] Drain pre-wash and fill tank with rinse water.
    [4] Partially submerge the tank into a running ultrasonic cleaner with degassed water for 2 mins.
    [5] Drain tank again and pull out the film snip.
    [6] Firmly wipe the snip with a while paper towel. No any visible black carbon trace could be found.

    Previously when I only used "pre-wash + vigorous agitation + rinses" method, there was still a very fine rem-jet layer of carbon left which can be detected by wiping with a white paper towel. I had to manually wipe the film base side again after the fix. Now it seems that I don't have to do it again due to this ultrasonic cleaning method. I suspect a plastic tank will not work well in this case.

  7. #7
    ektachrome's Avatar
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    I always wash the film in Household Soda, wipe with a Photo Chamois, and re-wipe with another chamois soaked in Photo-Flo.
    It never fails.
    Ektachrome

  8. #8
    holmburgers's Avatar
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    It's good to hear that people generally don't seem to have a problem getting this stuff off. From a technological elegance standpoint, I really like the idea of using ultrasonic cleaning!
    If you are the big tree, we are the small axe

  9. #9

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    Kodak PB-2 forebath for Rem-Jet removal

    For removal of the Rem-Jet backing on Kodak color motion picture films in Process ECN-2.

    Water (27 – 38C) 800 ml
    Borax (decahydrate) 20 g (or 15 g of pentahydrate)
    Sodium sulfate (anh) 100 g
    Sodium hydroxide 1 g
    Water to make 1 l

    pH at 25C = 9.25
    Replenish with the above solution

  10. #10

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    Kodak offers two alternate prebath formulas in the "Processing Kodak Motion Picture Films, Module 7, Process ECN-2 Specifications" document, available here:

    http://motion.kodak.com/motion/uploa...h247_h2407.pdf

    Attached below is a screen capture of that page.

    Duncan

    Click image for larger version. 

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