Cleaning Remjet/tar residue from UPB1A dev tank reels

Discussion in 'Color: Film, Paper, and Chemistry' started by philpem, Aug 12, 2018.

  1. philpem

    philpem Subscriber

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    I've just picked up a Lomo UPB-1A dev tank in fairly good condition -- some superglued cracks which haven't held, but it looks repairable.

    Problem is one of the reels is absolutely covered in what looks like Remjet or tar from chemical processing -- it's a black coating all over the reel.

    What's the easiest way to remove this mess from the reels? Solvent and scrub with a nailbrush or toothbrush, I guess, but what solvent would be appropriate?

    Thanks
    Phil
     
  2. lantau

    lantau Subscriber

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    It could be remjet residue or black residue left from colour developer. For both I use acid in combination with a brush. You'll definitely need mechanical force. Since I have sulfuric acid at hand I use that. The dilution is something you want to work out. Just don't use very highly concentrated acid. More in the range of 3-10% max.

    And you should have at least some clue about acids if you want to do that, obviously. I do it indoors, but if you are unsure do it outside. Eye protection is necessary as well as old clothing. Using a brush (or an old sponge cloth) will lead to droplets going your way sooner or later.

    Strong alkali might do it as well. But I consider alkalis to be more dangerous for the average user. Acid washes off the skin much quicker. If you were to get 100% sulfuric acid on your skin you just need to stay calm, proceed to the nearby watertap (don't run) and wash it off. No harm done. But do stay close to a source of water for washing off at all times.

    Oh and normal remjet removal solution (mild base at pH 10) will not work. Once treated with it, remjet becomes nasty sticky stuff. And that stuff will not be loosened again by that solution.
     
  3. mshchem

    mshchem Subscriber

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    From looking at this o Ebay, looks like the reel is general purpose polystyrene. No solvents or strong acids! I would clean best you could with a brush, dish soap and warm water. I have a 1940s vintage Bakelite tank (black thermoset used for tank) my Dad used epoxy glue on it, still intact.
     
  4. OP
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    philpem

    philpem Subscriber

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    Eep! I'm glad I tried a cloth and isopropyl alcohol (rubbing alcohol) as my first go...!

    As it turned out, most of the dirt was on the bottom of the reel, not in the grooves. A good hour spent rubbing the bottom of the reel with a cloth soaked in isopropyl took most of the dirt off (looked like carbon dust, so I'm guessing Remjet). A clean cloth run through the film track got rid of the last of it. It's now almost pristine :smile:

    Thanks for the suggestion of using epoxy for the repair - I was leaning that way as the superglue the previous owner used hasn't held. Hopefully Araldite will work fairly well, though I'm torn between that and J-B Weld. I might mix some carbon or black plastic into the Araldite as filler to try and cut down the risk of light leaks or shrinkage of the epoxy... though I'll have to do my "is this a good idea?" bookwork first!

    Looks like I'll have to do a bit of sanding afterwards, the two pieces which broke off don't quite fit in the gap; the one on the right is sitting at a slight slant. The top lid looks like an easy fix though, thankfully!
     
  5. lantau

    lantau Subscriber

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    Keep in mind that most solid polymere objects like your spiral will not just melt away because you get some acid onto it. According a stability table I've got, polystyrene is actually very stable in hydrochloric acid and sulfuric acid up to 20%, at 20°C. At 50°C in sulfuric acid it is only stable, not very stable.

    The short exposure for cleaning should be uncritical. I'd be more careful with any styrofoam, though.
     
  6. mshchem

    mshchem Subscriber

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    You can blend black plastic or carbon I wouldn't go over 20% loading. Plastics are routinely "filled" with minerals, fiberglass etc. The epoxy shouldn't have a lot of shrink
     
  7. OP
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    philpem

    philpem Subscriber

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    Fixed the tank the other day - Araldite worked great, but I ended up using two tubes of Z7 superglue debonder to remove the old glue.

    Everything's stuck together with Araldite now, and the pieces lined up almost perfectly (had to sand off some ridges and gaps along the top edge of the tank). No leaks! :D

    So I guess the next step will be to get my hands on some Super 8 film and develop it...
     
  8. darkroommike

    darkroommike Subscriber

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    Cleaning tar off developing racks, back in the day, Hope recommended Lysol Toilet Bowl Cleaner, the racks had stainless steel sidewalls but lots and lots and lots of rollers and nylon bearings, squirt the stuff on and the tar would just run off/ Not sure what it would do to styrene, but if all else fails you could try a drop of two. You wan the acid toilet bowl cleaner not the stuff with bleach and NEVER mix acid cleaners with bleach!
     
  9. pentaxuser

    pentaxuser Subscriber

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    Is this normal remjet solution to which you refer, stuff you buy or is this stuff that is made at home from ingredients that do not work? It sounds as if it changes the state of remjet from a solid substance to a stick substance which cannot be scraped off while sticky. What happens to the sticky remjet afterwards? Does it re-set and then not even become sticky again if you try and use the removal solution for a second time?

    Any help in clarifying my confusion is appreciated. Thanks

    pentaxuser
     
  10. fdonadio

    fdonadio Subscriber

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    It’s the pre-bath specified in Kodak’s documentation:


    Prebath 2 (PB-2)
    Water 27 to 38°C (80 to 100°F) ....... 800 mL
    Borax (Decahydrated) ................ 20.0 g
    Sodium Sulfate (Anhydrous) ................. 100 g
    Sodium Hydroxide ............... 1.0 g
    Water to make ............................ 1L
     
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