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  1. #1

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    Clearing pt/pd print

    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. #2

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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. #3
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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. #4

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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. #5
    clay's Avatar
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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. #6

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    Be careful of the time with HCA, because it will bleach the print if you go much past this.
    Hmmm...how did you find this out? Just being curious as I have never seen this mentioned before.

  7. #7

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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. #8
    clay's Avatar
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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.

    Quote Originally Posted by Jorge
    Hmmm...how did you find this out? Just being curious as I have never seen this mentioned before.

  9. #9
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    Clay, have you tried using 7-Up for a source of phosphoric acid?
    Diane

    Halak 41

  10. #10
    Kerik's Avatar
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    Quote Originally Posted by clay
    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.
    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...
    Kerik Kouklis
    Platinum/Gum/Collodion
    www.kerik.com
    2014 Workshop Schedule Online

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