Clearing pt/pd print

Discussion in 'Alternative Processes' started by eggshell, Dec 8, 2005.

  1. eggshell

    eggshell Member

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    I hope I'm not being irritating asking so many questions in recent days. If I am, please tell me so.

    I'm having trouble clearing prints. I'm using combination of sodium sulfite, HCA, and Citric acid to clear Platinotype and Cranes Kid Finish paper. Faint yellow brush marks persist to appear on the paper even after 30 min. clearing time. I'm mixing 1 to 1 1/2 tablespoon to 1 litre of water. Should I be using alternative clearing agents or use different paper? Thanks.
     
  2. eggshell

    eggshell Member

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    By the way, water temp. here is around 85 Degree f, so I think it's not too low for effective clearing. Thanks.
     
  3. clay

    clay Subscriber

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    Are you using a plain water clearing bath right after the developer?

    If you are, you may be having the same problem i had for a while. My tap water is pH positive - like about 7.5 or so. It was locking in the ferric. So I switched to the following procedure:

    1)leave print in the developer for 5 minutes, even though it does not appear to be doing anything. The developer will clear out a lot of the unused ferric.

    NO water soak

    2)5 minutes citric acid mixed at 1 heaping tablespoon per liter

    3)5 minutes of HCA mixed 1:3 instead of 1:4 mixed with a tablespoon of EDTA per liter of total volume

    4) 5 minutes in another tray of the HCA mixed identically

    Be careful of the time with HCA, because it will bleach the print if you go much past this.

    On the rare occasions this has not worked, I will use 1-2% phosphoric acid for bath #2

    Hope this helps.

    Clay
     
  4. eggshell

    eggshell Member

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    Clay, First thank you for the quick response.

    Yes, water bath after developer and in-between three clearing baths. I think double coating may also have added to the difficulty. Your suggestion that water supply may be the cause of the problem caught me by surprise. Never cross my mind! Printing again tomorrow. I will mix the clearing bath as you mentioned. If I can't get phosphoric acid, is there an alternative? Hope this works out! Thanks a million!
     
  5. clay

    clay Subscriber

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    If you don't have any phosphoric acid, and the other steps still don't clear it completely, try hot (110 degrees or so) citric acid at 2%. This can get sort of delicate, because too strong and too hot can bleach the print.

    Another thing I forgot to ask is if you mix in some oxalic acid with your ferric oxalate when you mix it into solution. It really helps promote clearing, plus speeds up your printing times by nearly a stop (My experience is that 4g oxalic/27g ferric oxalate/ in 100ml of water will make printing times about 60% of what they would be with ferric oxalate used alone)

    Another, nastier, option is to get some muriatic acid from the hardware store and mix it up at 1-2% for on of the baths. Be aware that it is corrosive and puts off a lot of fumes. Use adequate ventilation and get rid of it as soon as you are done. It will etch metal pipes in the area of the tray if you leave it sitting around in an open tray. Also, do not use it in conjunction with a sodium sulfite based clearing agent without a water rinse in between. The acid will convert the sodium sulfite to sulfur dioxide gas, and the rotten egg smell will not make you a popular person in your living space.

    I try to avoid using muriatic completely because of these problems. So far, the other steps I have outlined have worked just fine for even stubborn papers.
     
  6. Jorge

    Jorge Inactive

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    Hmmm...how did you find this out? Just being curious as I have never seen this mentioned before.
     
  7. avandesande

    avandesande Member

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    Muriatic acid and sulfuric acid will eat up your pipes.

    Phosphoric acid is much safer to handle and for your plumbing. I would try a pool store, i think the 'ph-down' type products are phosphoric acid.
    Also look in a hardware store for 'naval jelly', same thing.
    Just make sure to read the label to see if there are any undesirable additives.
     
  8. clay

    clay Subscriber

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    I got a phone call one time while a print was in a tray of HCA. When I came back 30 minutes later, it had lost at least one stop of density, if not more.

    Try it on a print sometime. You will be shocked. The thing to keep in mind is that if it bleaches noticeably at 30 minutes, there undoubtedly will be some harder-to-see bleaching that occurs at shorter times than this, but it is all a matter of degree.

    Any clearing regimen using HCA (or muriatic) should use the absolute minimum time it takes to get rid of the residual ferric, and no more.

     
  9. colrehogan

    colrehogan Member

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    Clay, have you tried using 7-Up for a source of phosphoric acid?
     
  10. Kerik

    Kerik Member

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    Problem is, this isn't easily defined since it will be different for different papers and for different temps, etc. Too little clearing will be worse in the long run. I've never noticed any bleaching from HCA, although I've never left a print in for 30+ minutes. No one ever calls me... :tongue:
     
  11. Jorge

    Jorge Inactive

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    Ha, weird...I routinly leave my prints for 15 minutes per bath for a total of 45 in HCA and have never noticed this. I think I am going to print a step wedge and check it out, it might be the reason I only get a Dmax of about 1.35.....live and learn!
     
  12. jimgalli

    jimgalli Subscriber

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    Newbie here, but I understand the palladium is more sensitive to HCA bleaching than platinum.
     
  13. clay

    clay Subscriber

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    No doubt that insufficient clearing is a much bigger problem than bleaching from HCA.

    And there is also no doubt that it is paper dependent. Doubters should try clearing double-coated Rives BFK sometime!

    Your point is correct - you just have to keep an eye on things and check clearing occasionally by masking your borders (or some area on the coated area of your print) I have seen a number of prints with 'show the brushstrokes' borders that probably are not completely cleared.



     
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  15. eggshell

    eggshell Member

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    Sorry for the delayed reply. I'm loosing a little sleep over this one. I got the kit from B&S, so I don't suppose there's oxalic acid in the bottle of ferric oxalate. Think I should purchase some and have it handy. Your question led me to investigate the New Platinum Book and I found that I can add EDTA Tetrasodium too. If yes, question is:

    1. Is EDTA Tetrasodium similiar to the Edta Clearing Agent B&S sent me?

    2. Is it okay now to add Edta to the already mix ferric Oxalate?

    3. Does Oxalic acid do a better job than Edta added to Ferric Oxalate solution?

    Next... Hope this isn't a dumb question, but does it make sense to alter the pH of the rinse/wash water by adding a little of "something" to it?

    I've got a nice print made a few days ago and I'm 100% sure it hasn't been cleared sufficiently. The print border isn't masked. With all the soaking in pH positive rinse/water baths, will it retard clearing action if I did re-clearing, following the procedure as you described earlier?

    Thanks again for being so helpful.
     
  16. eggshell

    eggshell Member

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    Actually I did looked at the content of Sprite can, and it said citric acid. Maybe I'll check 7-up. Thanks!
     
  17. eggshell

    eggshell Member

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    Good resource avandesande. Thanks to you too.
     
  18. Kerik

    Kerik Member

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    Answers:
    1.Yes.
    2.Yes, but probably not necessary.
    3.The EDTA seems to help the ferric go into solution, so adding it later won't do much. It's the oxalic acid that seems to help with printing speed and clearing.
    Next...yes, you could sprinkle some oxalic or citric acid into your rinse. Or, just follow the clearing process as Clay described.
    Finally, you can go ahead and re-clear the print starting with step 3. in the procedure that Clay outlined above. Did you tell us what paper this print is on?
     
  19. eggshell

    eggshell Member

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    Thanks for the answers, Kerik. Really appreciate it! The print I need to re-clear is made on Platinotype paper. I will try to re-clear the print using those steps but there's no way of telling if it clears completely since the border wasn't masked.

    Now for the good news. I double-coated two strips (full strength & half strength), one on platinotype, the other, Cranes Kid Finish paper. After drying, I immersed the two unexposed strips into the usual Pot. Ox. developer. Removed the strips after 5 min. Some stains could be seen. They went immediately into 1st HCA/Edta bath. Within 3 min. the stains are completely gone. It worked! Lesson learnt!!

    Thank you very, very much Clay. I wouldn't know how to fix the problem without asking for help. Newbies like me can really benefit from you, Kerik, Jorge and others. I am humbled by your experiences.

    Thanks to all.
     
  20. eggshell

    eggshell Member

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    Oh yeah, I forgot to mention the strip went into citric acid bath before 1st HCA/Edta bath. There was still a faint stain after citric acid bath, and cleared completed within 3 min. in HCA/Edta bath.

    I'd glad I need not have to handle stronger acids. Thanks again.
     
  21. clay

    clay Subscriber

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    The only reason we know any of this stuff is because we were humbled by experience! In alt process stuff, just like most things in life, the moment you think you have it figured out, the flying spaghetti monster intervenes and makes you feel like a fool.

    http://www.venganza.org/

     
  22. eggshell

    eggshell Member

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    Okay! Remember the print I want to re-clear? I recreated the same condition as the processed print on a new test strip: Develop an unexposed test strip, rinse, clear, rinse, clear, dry the strip with an anticipated stain.

    I tried re-clearing this stained strip using the method outlined above (even at 110F). Outcome: It didn't clear too well. Not yellow stains, more like water mark stain. What's trapping the stain? Thanks again.
     
  23. wm blunt

    wm blunt Member

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    Might be fogging instead of a clearing problem.
     
  24. eggshell

    eggshell Member

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    Wm, do you mean my ferric oxalate might have turned bad? It's 2 months old. Refrigerated when not in use. Thanks.
     
  25. Jorge

    Jorge Inactive

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    2 months old is not too old for FO. Are you using the evil #2 FO in your mix or not? If you are not using the restrainer sometimes you get fogging. You might want to add one drop to avoid fogging.
     
  26. eggshell

    eggshell Member

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    Hi Jorge, I don't use #2 FO. I've read about the fogging. Maybe that's the problem. But somewhere it doesn't add up. My earlier test without water rinse in between developer & clearing bath as instructed by Clay, cleared effectively. Hm...