Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,279   Posts: 1,534,854   Online: 763
      
Page 3 of 6 FirstFirst 123456 LastLast
Results 21 to 30 of 60
  1. #21
    Kerik's Avatar
    Join Date
    Nov 2002
    Location
    California
    Shooter
    Medium Format
    Posts
    1,465
    Images
    238
    Vaughn you are correct. Heating the developer releases water vapor resulting in an increased concentration. The crystals indicate the solution is beyond saturation at room temp. You can either add water (distilled or deionized) until they dissolve or simply filter them out then add fresh developer which is what I usually do. The actual concetration of the developer is not that critical. It is a good idea to filter out the black grit fairly regularly because it can sometimes stain the paper.

    You should also monitor the pH of your PO with litmus paper (a pH meter is more accuracy than you need, and they break too easily). I like to keep my PO around pH 6 by adding small amounts of oxalic acid. Once the developer becomes alkaline (pH 7 or more) it can have a detrimental effect on the print quality. You can also do as Dennis suggests and sprinkle in some oxalic acid once in a while and not worry about the litmus paper.

    It ain't rocket science, so don't worry about being too anal about this stuff. Some basic maintenance will keep your developer going for a long, long time.
    Kerik Kouklis
    Platinum/Gum/Collodion
    www.kerik.com
    2014 Workshop Schedule Online

  2. #22
    Kerik's Avatar
    Join Date
    Nov 2002
    Location
    California
    Shooter
    Medium Format
    Posts
    1,465
    Images
    238
    Quote Originally Posted by Jarvman View Post
    Yeah I'm a bit gutted that I've got the citrate now instead of the oxalate. I phoned up B&S but the price for shipping one bottle is rediculous. :-( Is there any where in this country I can source it? Should have bought some off Paul and Max when I was up there. They are working on an exhibition in Italy soon showcasing 21 years of their work at the mo.
    Jarvman it's easy to make your own PO from potassium carbonate and oxalic acid if you can get those chemicals locally.

    (You may want to do this outside or at least with good ventilation as the process gives off CO2, some heat and a significant amount of bubbles. Think gradeschool volcano project.)

    To make 2 Liters:

    1. Start with about 1100 ml cold distilled water in a container big enough to handle all the effervesence - maybe a gallon or two.

    2. Add 450 grams of Potassium Carbonate mono with stirring until dissolved.

    3. SLOWLY add 400 gm of oxalic acid to the potassium carbonate solution with stirring, waiting each time you add the acid until the bubbling subsides. Continue until all of the oxalic acid has been added.

    4. Add water to bring total volume to 2 liters. Check the pH at this point. It should be near 7.0 (neutral). Now add more oxalic acid in small amounts and keep checking the pH. When you get the pH to about 6.0, you’re done.
    Kerik Kouklis
    Platinum/Gum/Collodion
    www.kerik.com
    2014 Workshop Schedule Online

  3. #23
    dpurdy's Avatar
    Join Date
    Jun 2006
    Location
    Portland OR USA
    Shooter
    8x10 Format
    Posts
    2,043
    Images
    38
    Quote Originally Posted by Kerik View Post
    J
    To make 2 Liters:

    1. Start with about 1100 ml cold distilled water in a container big enough to handle all the effervesence - maybe a gallon or two.

    2. Add 450 grams of Potassium Carbonate mono with stirring until dissolved.

    3. SLOWLY add 400 gm of oxalic acid to the potassium carbonate solution with stirring, waiting each time you add the acid until the bubbling subsides. Continue until all of the oxalic acid has been added.

    4. Add water to bring total volume to 2 liters. Check the pH at this point. It should be near 7.0 (neutral). Now add more oxalic acid in small amounts and keep checking the pH. When you get the pH to about 6.0, you’re done.
    Is the advantage to this in the cost? Or just easier than having it shipped?
    Dennis

  4. #24
    Kerik's Avatar
    Join Date
    Nov 2002
    Location
    California
    Shooter
    Medium Format
    Posts
    1,465
    Images
    238
    If you buy the chems in reasonable quantity it's much cheaper this way.
    Kerik Kouklis
    Platinum/Gum/Collodion
    www.kerik.com
    2014 Workshop Schedule Online

  5. #25

    Join Date
    Sep 2006
    Location
    Cardiff, United Kingdom
    Shooter
    Multi Format
    Posts
    736
    Images
    68
    It's £6.99 for 100g of oxalic acid from retro so its going to work out more expensive this way. there's a chemical company called sigma aldrich that sell everything but you need a business account with them apparently. I never got the chance to try a gradeschool volcano project
    Last edited by Jarvman; 02-27-2009 at 02:48 PM. Click to view previous post history.

  6. #26

    Join Date
    Jul 2003
    Location
    Texas
    Shooter
    Multi Format
    Posts
    3,576
    Images
    27
    Jarvman, check with one of the woodcare type shops. Some carry oxalic acid to bleach/clean wood products. Here is a link to a place I found using google and it is 8.75 inc VAT for 1Kg.
    Mike C

    Rambles

  7. #27
    Kerik's Avatar
    Join Date
    Nov 2002
    Location
    California
    Shooter
    Medium Format
    Posts
    1,465
    Images
    238
    Yeah, you need to find a chemical supplier that will sell in much larger quantities. There are many here in the states like The Chemistry Store:

    http://www.chemistrystore.com/Chemic...alic_Acid.html
    http://www.chemistrystore.com/Chemic...Carbonate.html

    I buy the chems from a local place that sells pool chemicals and the like to the public.
    Kerik Kouklis
    Platinum/Gum/Collodion
    www.kerik.com
    2014 Workshop Schedule Online

  8. #28

    Join Date
    Sep 2006
    Location
    Cardiff, United Kingdom
    Shooter
    Multi Format
    Posts
    736
    Images
    68
    ooh ooh, another thing, how many of you actually presoak your paper before coating it? Leaving it to dry out before applying the pt/pd obviously.

  9. #29

    Join Date
    Mar 2005
    Shooter
    ULarge Format
    Posts
    868
    Images
    24
    It depends on the paper. I don't presoak unless the paper is too alkaline, in which case it gets an acid pre-soak.

  10. #30
    donbga's Avatar
    Join Date
    Nov 2003
    Shooter
    Large Format Pan
    Posts
    2,058
    Quote Originally Posted by Kerik View Post
    Vaughn you are correct. Heating the developer releases water vapor resulting in an increased concentration.
    FWIW, I use a large - 2 QT. Pyrex measuring cup with plastic lid to heat my PO. The lid minimizes evaporation and the vapor condenses on the inside of the lid.

    As Kerik said filter the sludge and check the pH. Top off with fresh PO as the volume declines or add a little water to dissolve crystals at the bottom.

    You are good to go.
    Don Bryant

Page 3 of 6 FirstFirst 123456 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin