Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,950   Posts: 1,585,960   Online: 922
      
Page 2 of 2 FirstFirst 12
Results 11 to 20 of 20

Thread: Ferric Oxalate

  1. #11
    clay's Avatar
    Join Date
    Nov 2002
    Location
    Asheville, North Carolina
    Shooter
    Multi Format
    Posts
    1,124
    Images
    8
    Unless you are using di-sodium EDTA, you may not be clearing the paper. The more commonly available tetrasodium EDTA has a basic pH, and if used alone, will lock the ferric into the paper for keeps. I would always make sure that your first clearing tray has a clearing solution with a pH below 7 - whether that is citric acid, phosphoric acid, di-sodium EDTA or muriatic. If you hit that just-developed paper with a basic (pH>7) solution, you are going to be creating only headaches for yourself.

    Quote Originally Posted by Andrew O'Neill View Post
    I spent all day in my darkroom. I mixed up the sensitizer and brushed it on my paper. Exposed for about 7 minutes, developed in sodium citrate, cleared in EDTA (I didn't have any citric acid), and fixed. Didn't bother with toning. I'll worry about that when I nail down exposure/dev and processing.

    Just by looking at the print I can tell that I over exposed it. The highlights are too dark. I backed off on the exposure quite a bit but highlights still have slight reddish/brown tinge. Is this the stain that needs to be removed by the clearing bath? Is citric acid better than EDTA? The paper I used was good for Van Dykes...I even gelatin sized it.

    Also, the darkest areas are a bit spotty...not grainy...detail is lost. Any ideas what could be causing this?

    Man this is hard when one is on ones own and one has no real kallitype to look at...
    I just want to feel nostalgic like I used to.


    http://www.clayharmon.net - turnip extraordinaire

  2. #12
    Andrew O'Neill's Avatar
    Join Date
    Jan 2004
    Location
    Coquitlam, BC, Canada
    Shooter
    8x10 Format
    Posts
    701
    Images
    9
    The print is actually not grainy...just a bit spotty in some places. After careful examination, the spottyness appears to be the texture of the paper. I read somewhere that gelatin sizing is supposed to help increase Dmax...this paper worked well when I did Vandykes.
    Does anyone know if humidity is important? The humidity was about 70 in my darkroom. Thanks for all your help.

  3. #13
    Andrew O'Neill's Avatar
    Join Date
    Jan 2004
    Location
    Coquitlam, BC, Canada
    Shooter
    8x10 Format
    Posts
    701
    Images
    9
    Thanks for that info, clay. Very interesting.

  4. #14

    Join Date
    Jul 2003
    Location
    Portland - Oregon
    Shooter
    Large Format
    Posts
    91
    Images
    12
    Quote Originally Posted by clay View Post
    The more commonly available tetrasodium EDTA has a basic pH, and if used alone, will lock the ferric into the paper for keeps.
    If all you have is the tetrasodium version, a solution with equal spoonfulls of tetrasodium EDTA and sodium bisulfite or metabisulfite will give you a pH of about 6.5.

    Alan

  5. #15

    Join Date
    Jul 2003
    Location
    Portland - Oregon
    Shooter
    Large Format
    Posts
    91
    Images
    12
    Quote Originally Posted by Andrew O'Neill View Post
    Does anyone know if humidity is important? The humidity was about 70 in my darkroom.
    Yes, the relative humidity in your darkroom is very important! A relative humidity of 70% is envyable. When I started coating this winter I purchased a wet-dry bulb hygrometer and the RH varies between 85% on wet days and 65% on dry days. I'm waiting to see what summer will bring.

    I see we both live on the west coast.

  6. #16
    clay's Avatar
    Join Date
    Nov 2002
    Location
    Asheville, North Carolina
    Shooter
    Multi Format
    Posts
    1,124
    Images
    8
    Yep. the bisulfite is acidic and will lower the pH. That is why homebrew hypoclear needs this in addition to the sodium sulfite to be effective in clearing. Good point!

    Quote Originally Posted by Alan Davenport View Post
    If all you have is the tetrasodium version, a solution with equal spoonfulls of tetrasodium EDTA and sodium bisulfite or metabisulfite will give you a pH of about 6.5.

    Alan
    I just want to feel nostalgic like I used to.


    http://www.clayharmon.net - turnip extraordinaire

  7. #17

    Join Date
    Oct 2005
    Location
    Pakistan
    Shooter
    Multi Format
    Posts
    266
    Let me come back to the non-dissolving FO: could it be that what does not go into solution is just ferrous oxalate? In powder form, it looks just the same!

    A text to find out is: forget about heating the FO, but make up some concentrated oxalic acid by heating that, pur a little into the would-be solution, add some peroxide dropwise until a visible reaction occurs, stir, repeat until the content in the beaker becomes an amber-coloured, transparent solution. Then test for traces of ferrous.

    If this works, you had a significant amount of ferrous oxalate in your batch (which you now removed in the solution).

  8. #18
    Andrew O'Neill's Avatar
    Join Date
    Jan 2004
    Location
    Coquitlam, BC, Canada
    Shooter
    8x10 Format
    Posts
    701
    Images
    9
    Thanks guys, for all your help. I've been in the darkroom playing around with the process and love it. It doesn't always work but when it does...since I've got a ton of EDTA of the wrong type, I'll try adding sodium sulfite to it. Thanks!
    I like using sodium citrate as the developer. Ran out of it so tried a combo of rochelle salt, borax, and tartaric acid (lots of borax and very little rochelle salt)...really nice colour but I think I'll stick with sodium citrate when it ever decides to arrive at my door.

    One observation I've made:

    Prints that are exposed and process soon after coating (dry but cool to the touch) seem to clear faster.
    coated papers that had a good day sitting in the dark before exposure and processing seemed to take much much longer to clear or not totally clear at all. Also, upon pouring in the developer on the exposed print I noticed that some of the coating on areas outside of the negative had a washed out look.
    Has anybody noticed this before?

    And a question:

    I work under a safelight and a very weak tungsten light...how bright can I have my darkroom when coating and processing? It's difficult to see if paper has totally cleared unless I put the light up bright.

    One more question:

    When will all this bloody rain END?? Alan, are you getting lots of rain down there??

  9. #19

    Join Date
    Jul 2003
    Location
    Portland - Oregon
    Shooter
    Large Format
    Posts
    91
    Images
    12
    Quote Originally Posted by Andrew O'Neill View Post
    Also, upon pouring in the developer on the exposed print I noticed that some of the coating on areas outside of the negative had a washed out look.
    Has anybody noticed this before?

    ...how bright can I have my darkroom when coating and processing? It's difficult to see if paper has totally cleared unless I put the light up bright.

    When will all this bloody rain END?? Alan, are you getting lots of rain down there??
    Andrew,

    Are you leaving enough paper around the margins of your image in order to extend the coating out away from the image? If not you may be thinning out the coating near the edges of your image.

    I have one 60w bug light over my coating area and another as a general room light screwed into the ceiling.

    It has nice here Thursday but it has been raining most of today. It is supposed to rain through the weekend and on into next week.

    Alan

  10. #20
    Andrew O'Neill's Avatar
    Join Date
    Jan 2004
    Location
    Coquitlam, BC, Canada
    Shooter
    8x10 Format
    Posts
    701
    Images
    9
    rain rain...nothing but rain...oh well.

    Yes, I'm leaving plenty of room outside of the image area. I tried again this morning and it didn't happen...gremlins, I tell ya.
    I sorted out the yellow staining...If my exposures are too long it happens. I'll have to do more testing at the negative side of things. I'm developing my film in pyrocat-HD. I'll have to cut way back on dev time. My xtol developed negs print nicely. More testing. Perfect for weather like this!

Page 2 of 2 FirstFirst 12


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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