Any one ever have this Problem with COT 320

Discussion in 'Alternative Processes' started by Paul, Sep 21, 2006.

  1. Paul

    Paul Member

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    I have a pack of COT 320 in 11X14 that I am using for kallitypes. Some of the sheets seem to have an imperfection. Every once in a while a strip about 2 inches wide running the short length of the paper ends up a different color than the rest of the print. I suspect that it is taking the coating too well and then not clearing. It is not a super dramatic flaw, and toning reduces its appearance; however it is enough to ruin the print in my estimation. And, at $2 a sheet it is a pain in the wallet.

    It could well be that all of the sheets are like this and I simply get lucky when I cut them down to fit in my print frame and sometimes cut off the offending end. It is far too regular to be a brush stroke or anything of my making. Anyone else ever see this?

    At any rate, I just ordered some Arches Platine. Shame too, because COT 320 is so pretty when it works.

    -Paul
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    Paul, I have had some uniformity problems from batch to batch on this stuff, and it is hart to tell which side has the gelatin subbing on as well. The gelatin coating is so thin, you often don't know whether you are using the front or back.

    My uniformity problem shows up more as bubbles and spot imperfections.

    PE
     
  3. Paul

    Paul Member

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    PE,

    I have noticed that it takes a particular quality of light to reveal the difference between the smooth side and the not so smooth side. I usually have to hold them up to the window at an angle. I am quite sure that I was printing on the smooth side. Perhaps there is missing gelatin and this is allowing the coating to penetrate more deeply than in other areas?

    -Paul
     
  4. colrehogan

    colrehogan Member

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    I can tell the difference between the sides with my fingers. I coat the smooth side. Paul, I have never had any of my COT 320 do what you are describing.
     
  5. Monophoto

    Monophoto Member

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    Others have suggested the possibility that this could reflect coating on the wrong side of the paper. Perhaps. But there is a trick to telling the front of the paper. When it is produced, the "front" is up, so when the paper is stacked and trimmed, the trimming blade cuts the stack from top to bottom - or from front to back. This causes the edge of each sheet to have a profile that can be detected by gently feeling with a finger - a rounded end on the face or "front", and a sharp edge on the back. If you feel both sides (gently - - - gently), you can clearly sense the difference.

    Another possibility could be related to how the paper is coated. You didn't mention whether you used a brush or a rod - I have found that coating with a rod sometimes can cause more material to be applied on one end or the other if the rod is not moved at a uniform rate.
     
  6. Photo Engineer

    Photo Engineer Subscriber

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    Just FYI, after 30+ years coating, I have trouble with COT320 and cannot tell which is the right surface with 100% accuracy. Also, I use my coating blades to apply the emulsion.

    PE
     
  7. Paul

    Paul Member

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    I used a brush to apply the coating. The defective area in question is far too uniform, straight and parallel to the edge to be the result of a brush stroke. I think I have used about fifteen or so of the sheets and this has happened about three times.
     
  8. Joe Lipka

    Joe Lipka Member

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    I'm with Diane. I can feel the difference between the smooth and rough side with my fingers. Either that or I have been one of the luckiest guessers on the planet.
     
  9. donbga

    donbga Member

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    My experience with Cot 320 is that it is very easy to tell the difference between the smooth side and rough side just as Joe and Diane have mentioned. I've been using Cot 320 for several years and never had a problem with the paper.
     
  10. TheFlyingCamera

    TheFlyingCamera Membership Council

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    I too would say it sounds like you just got a bad batch or something, as I have no problems telling the sides apart by feel, and have not had the coating issue you are experiencing. I coat my Pt/Pd with a Richeson "Magic brush", and have coated on all sizes from 8x10 to 20x24 (cut down to 10x12 or 12x20 sheets).
     
  11. juanito

    juanito Member

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    I use only cot 320 for pt/pd. I coat sometimes the smooth side and sometimes the rough side, it depends if I want more or less texture. I didn't have any problems with it. I think it's a great paper.
     
  12. philsweeney

    philsweeney Member

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    for kallitype I have found quite a few papers that do not work well and many do not work well when double coated. I have found COT-320 to be the most friendly and double coats well. I hope you do not have a funky batch!