Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,840   Posts: 1,582,549   Online: 1021
      
Page 1 of 3 123 LastLast
Results 1 to 10 of 27

Thread: Pyrogallic acid

  1. #1

    Join Date
    Sep 2002
    Location
    Central Texas
    Shooter
    ULarge Format
    Posts
    67
    Hello, I bought a bottle of Pyrogallic Acid from Bryant Labs over a year ago and am getting close to an empty bottle. I recently purchased a new supply from Mike at Artcraft Chemicals. The Grade of the old bottle is "Crystal, Technical" and the grade of the new stuff from Artcraft is "Analytical Reagent 99.8% min. purity, powder". I didn't start using ABC pyro until this summer and when I did I was surprised to find that when I mixed my chemicals as others do my film had enough density to view the Sun with the Hubble. I had to dilute my chemistry to about 1:1:1:20 rather than the more common 1:1:1:7. Can the different Grades be enough to cause this difference in dilution? As far as I can tell everything else is similar to the way others use these chemicals except maybe that I use constant aggitation(I don't remember right now if that is different or not).
    huh?

  2. #2
    c6h6o3's Avatar
    Join Date
    Oct 2002
    Shooter
    Large Format
    Posts
    3,194
    Images
    6
    What film did you develop in it and for how long?
    Jim

  3. #3

    Join Date
    Sep 2002
    Shooter
    Large Format
    Posts
    4,530
    David this is a hard question as little amounts of pyro make a big change. Typically technical grade chemicals are in the 94 to 96% purity, so I find hard to beleive that a 2% difference in purity has made such a big difference in your developer strenght. But with pyro it could be possible. On th other hand how about your C solution, have you changed this? could you have made a mistake and mixed this stronger? Sodium carbonate is usually the culprit for things like this.
    One more thing, could you have made a mistake when mixing sol A?
    If you are using 1:1:1:20 then you would have oxidation very quickly in the developer. Have you seen streaks? have you seen more overall staining? examine all of this and let me know.




  4. #4

    Join Date
    Sep 2002
    Location
    Austin, Texas
    Posts
    132
    I am not a chemist, so take this as opinion only: pyrogallol is crystalline in nature. The powder form is simply pulverized crystals, so there should be no difference between the two forms in effectiveness as a developer. But be careful not to breathe the powder.

  5. #5

    Join Date
    Sep 2002
    Location
    Tijeras, NM
    Shooter
    Medium Format
    Posts
    1,246
    I have seen tremendous differences in the way films react with pyro, unless we know what film he was using it's hard to guess what is going on..
    Aaron
    art is about managing compromise

  6. #6

    Join Date
    Sep 2002
    Location
    Central Texas
    Shooter
    ULarge Format
    Posts
    67
    Hello, and thanks for your responses. The film that I have been using is HP5+. It sounds like you are saying that I have to be real careful when I mix my chemicals. I have always thought that if a little is good then a little bit more can only be better. I have really had to restrain myself with this stuff. Having thoroughly flunked college chemistry many years ago, I was wondering about the grades. If one is crystal and one is powder then it looks like the powder could absorb more water and then be less potent per weight??? Of course, they both look like powder to me.
    As far as streaking goes, I don't really know for sure. I have had some of this but I was passing it off as bad technique or other mistakes, mainly because I was using what I thought was a large volume. Depending on the amount of film, anywhere from 2500ml to 4000ml.
    At one point I thought that I had too much sol. C and so I reduced it for a couple of sheets and they turned out flat, but still as thick as kevlar.
    When I first started with ABC pyro I didn't really do any formal testing. I just sorta started using it to get a feel for it. (I know what you're thinking,"that sure is a powerful tool to be in the hands of a moron") The first couple of sheets that I processed were thick enough to require me to hold a 300 watt Reflector Flood about twelve inches above the film for at least 60 seconds to get a decent amount of density in the print.
    Things have improved somewhat and I will soon be out of HP5+ and will be using BPF200.
    huh?

  7. #7

    Join Date
    Sep 2002
    Shooter
    Large Format
    Posts
    4,530
    It sounds to me you have high overall staining as opposed to proportional staining. Since you are able to see different contrast when using different amounts of C.
    No, if a little bit is good a lot more is not better. So maybe you put too much pyro in solution A. One way to reduce the overall staining is to increase the sodium sulfite amount. Try increasing solution B. HP5+ is known for producing a higher overall staining than most films in pyro, so maybe your change to Bergger will help.
    Another cause could be overexposing the negative. What EI are you using? Most people rate HP5+ at 160 to 200 but maybe your meter/developer/temp combination requires that you rate the film higher.



  8. #8
    c6h6o3's Avatar
    Join Date
    Oct 2002
    Shooter
    Large Format
    Posts
    3,194
    Images
    6
    If you're holding a 300 watt lamp that close to the printing frame then your negatives are too dense. Way, way too dense. No error in film rating or agitation procedure could account for such a difference. The densest negative I have gets 25 seconds on Grade 2 Azo with the lamp 3.5' away. Since the intensity of the light falls off proportionally to the square of the distance, just moving the lamp from 1' away to 3.5' away is equivalent to about 3.5 f-stops. Then you're giving it at least double my maximum. That's another stop. So you're at least 4 stops denser than my most bulletproof, contrasty negative. That's assuming that you're getting a good black at 60 seconds.

    Have you developed any with the pyro you got from Mike? I bet that will solve your problem. Are you mixing it according to Michael Smith's instructions?
    Jim

  9. #9

    Join Date
    Sep 2002
    Shooter
    Large Format
    Posts
    4,530
    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (c6h6o3 @ Nov 17 2002, 10:37 PM)</td></tr><tr><td id='QUOTE'>No error in film rating or agitation procedure could account for such a difference.
    </td></tr></table><span id='postcolor'>
    I disagree, if David is rating the film at 100 and the EI he needs is 400 then there is two stops right there. If this is compounded with high overall staining for which HP5 is known for, I can easily see a 4 stop difference in density. I use HP5 as well as TMY 400 for my 8x10 and see a marked difference in overall and b+f staining between both films, HP5 being much greater than TMY.

    As I understand it he is already using the pyro from Artcraft, thus his questions about the purity grade. I believe the problem lies with the mixing of the chemicals. Without knowing how much David put in each solution the most likely problem is oxidation of pyro and high overall staining.


  10. #10
    c6h6o3's Avatar
    Join Date
    Oct 2002
    Shooter
    Large Format
    Posts
    3,194
    Images
    6
    I was being conservative. The level of density he&#39;s talking about goes way beyond anything attributable to stain.

    BTW, I get more fog stain with Bergger than with HP5+. This is probably due to the longer development times.
    Jim

Page 1 of 3 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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