Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,545   Posts: 1,572,836   Online: 1013
      
Page 13 of 32 FirstFirst ... 37891011121314151617181923 ... LastLast
Results 121 to 130 of 317
  1. #1
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    16,394
    Images
    148

    Modern Rodinal Substitutes Part II

    Apologies for having to start a new thread but I can't read or even access the first to reply to posts.

    So with a bit of telepathy

    Quote Originally Posted by Kirk Keyes View Post
    Well, there's a problem there, as it's really hard to measure pH accurately when it gets much above 12.5 or so. You have to start getting special electrodes and the like.

    But for MSDS work, it doesn't have to be too precise.
    __________________
    Kirk

    A point that's being missed is that A&O give a figure of 2.7% Potassium Hydroxide not 3% in older Agfa MSDS.

    The pH is around 14 sure, but the actual requirement is the pH of the working dilute solution rather than the concentrate which is given elsewhere as pH 11.55, which I commented on in the first post of the thread.

    Way back Ron (PE) mentioned adjustments to Rodinal before bottling, the question we need to ask is are they adjusting on the basis of the concentrate, or also doing some tests on a dilute sample, as this will be a far more accurate indicator.

    Can someone please post a link to this continuation on the original post.

    Ian

  2. #121

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    Quote Originally Posted by Photo Engineer View Post
    Old style developers were washed to a given conductivity, and this was done after the treatment with sulfur.
    You probably mean "Old style emulsions" and not "Old style developers".
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  3. #122

    Join Date
    Aug 2005
    Location
    Earth
    Shooter
    Multi Format
    Posts
    1,560
    Quote Originally Posted by Kirk Keyes View Post
    You probably mean "Old style emulsions" and not "Old style developers".
    without a doubt...

  4. #123
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,391
    Images
    65
    Fixed. Thanks.

    PE

  5. #124

    Join Date
    Aug 2005
    Location
    Earth
    Shooter
    Multi Format
    Posts
    1,560
    Quote Originally Posted by Photo Engineer View Post
    An important note regarding old and new emulsion types has been bothering me regarding the evolution of the Rodinal developers and several other formulations.
    <cut>
    PE
    I really don't think I can totally agree with everything said in your orignal post; I can see how the silver halide solubility could be potentially different, due to new grain structures and halide profiles, possibly even affecting the deposted silver and its solubilty, but your other claims of "exotic" sulfur compounds and vastly differing color senstizers really need more comment...

    Ray

  6. #125
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,391
    Images
    65
    Ray;

    Just converting from conductivity to vAg will change the excess halide available to diffuse into the developer at the start of the process. Using an organic antifoggant or antioxidant instead of Sodium Sulfite in an overcoat will change emulsion properties and use of Thiosulfate as sensitizer instead of Thiocyanate will change the properties.

    Modern sensitizing dyes are quite different than the early dyes and we both know that. Examples are modern cyanines and merocyanines and earlier ones include many ortho dyes instead of pan dyes. Erythrosine comes to mind here.

    So, I'm sure with some thought, we all could come up with a long long list of simple differences that are quite well known having been posted here before and posted elsewhere.

    PE

  7. #126

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    But how much effect would these ancillary compounds really have on the development of films? And in what ways?
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  8. #127

    Join Date
    Aug 2005
    Location
    Earth
    Shooter
    Multi Format
    Posts
    1,560
    Quote Originally Posted by Photo Engineer View Post
    Just converting from conductivity to vAg will change the excess halide available to diffuse into the developer at the start of the process.

    Modern sensitizing dyes are quite different than the early dyes and we both know that. Examples are modern cyanines and merocyanines and earlier ones include many ortho dyes instead of pan dyes. Erythrosine comes to mind here.

    PE

    Re Conductivity vs VAg...
    For the most part, arn't they both aimed at getting one to the same point?
    I thought conductivity was used to estimate the degree of washing...
    and infered a certain desired the pX from that.
    I had the idea that VAg was just a more accurate measure....
    and that the desired point would be the same despite which method was used to get there.

    Re Dyes
    For the triphenylmethane dyes, etc., yes I agree.
    Somehow I thought you were thinking of something newer.

    Ray

  9. #128
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,391
    Images
    65
    Ray;

    Firstoff, one never measures pX. You cannot infer much of anything from it. You need vAg or pAg to measure the free Silver ion present as it is the critical item and varies with halide. Conductivity is not a measure of either when you get down to it.

    As for dyes, sure I can throw in an Osmate dye complex just for fun.

    PE

  10. #129

    Join Date
    Aug 2005
    Location
    Earth
    Shooter
    Multi Format
    Posts
    1,560
    Quote Originally Posted by Photo Engineer View Post
    Ray;

    Firstoff, one never measures pX. You cannot infer much of anything from it. You need vAg or pAg to measure the free Silver ion present as it is the critical item and varies with halide. Conductivity is not a measure of either when you get down to it.
    Well, pAg and pX are related of course...
    and while pAg is of interest, is it not the AgX solublity that is really the important consideration when conductivty is being measured, ie just prior to CD?

    If so, then the halide concentration should be of interest... in anycase you are right, conductivity is not really a measure of either pAg or pX,
    but... they both change with progressive wash efectivness and therefore their former? usefulness as a guide.

    ---

    Re the extra fun Osmate dye complex...
    On no, lets wait a while!
    I don't want to over dose!

    Ray

  11. #130

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    Ray - if you've been following along for the last couple years, you would have remembered that pX is useless when there is a mixture of halides in the system. What does that number tell you when there's a mixture?

    Thus, pAg is measured instead.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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