Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,943   Posts: 1,557,603   Online: 1277
      
Page 4 of 17 FirstFirst 1234567891014 ... LastLast
Results 31 to 40 of 162
  1. #31
    Marco B's Avatar
    Join Date
    Jan 2005
    Location
    The Netherlands
    Shooter
    Multi Format
    Posts
    2,983
    Images
    169
    Some links to organizations involved in art conservation that you may find useful to explore:

    http://www.conservation-us.org/
    http://www.cci-icc.gc.ca/index-eng.aspx
    http://www.incca.org/
    http://www.getty.edu/conservation/
    http://www.campbellcenter.org/pages/resources.html

    And you may find this page revealing and handy, from the Watercolors page on the Handprint webpage:
    Doing your own lightfastness tests

    And especially the results of light fastness tests of specific coded pigments as summarized here:
    Summary of 100 common pigments: http://www.handprint.com/HP/WCL/palette1.html

    and detailed info here:
    Detailed summary of 750 pigments: http://www.handprint.com/HP/WCL/waterfs.html

    if you think the above test isn't relevant (it's about watercolor paint mainly), than realize that watercolor paints are actually paints without any significant amount of binder like oil, so almost pure pigment. Hence testing watercolor will at least give you a "worst case" result for the stability of the pigment involved and probably faster test results.

    Marco
    Last edited by Marco B; 05-11-2011 at 12:36 PM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  2. #32
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,421
    Images
    2
    Marco,

    Why do I always pick the worst examples?? I admit that my statement about Vermeer was backed by absolutely zero research... just seemed like a convenient example of an old artist with vivid colors.

    Fascinating read though!
    If you are the big tree, we are the small axe

  3. #33
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,199
    Images
    65
    Marco;

    Don't forget George Eastman House as an organization that is concerned with conservation and restoration.

    PE

  4. #34
    Marco B's Avatar
    Join Date
    Jan 2005
    Location
    The Netherlands
    Shooter
    Multi Format
    Posts
    2,983
    Images
    169
    Quote Originally Posted by Photo Engineer View Post
    Marco;

    Don't forget George Eastman House as an organization that is concerned with conservation and restoration.

    PE
    Yes, sorry, you are completely right. These were just the bookmarks from my "Art" collection of bookmarks, not the "Photography" department:

    https://www.imagepermanenceinstitute.org/
    https://ritdml.rit.edu/

    But since we were also talking pure pigments, I thought the other links potentially very useful as well, and maybe in some ways even more relevant in that context.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  5. #35
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,421
    Images
    2
    Over the weekend I did a very quick & dirty test with a cyan carbon print. I did everything wrong; no safe edge (severe frilling), black-lights were too close so I got uneven exposure, etc. BUT, I did achieve my very first carbon print!

    I also did not wash it very thoroughly and the strangest thing has happened in the intervening days; a orangeish stain has manifested. I'm guessing that I did not wash out the sensitizer, but I'm curious what this is. The working instructions will probably lend some clues.

    It was transferred to Kodak dye-transfer paper actually, and I don't know if that mordant would have an effect.

    I can post it, though I'd prefer to show a better example once I work out the kinks.
    If you are the big tree, we are the small axe

  6. #36
    CMB
    CMB is offline

    Join Date
    Mar 2011
    Location
    Santa Cruz, CA
    Shooter
    Multi Format
    Posts
    89
    Chris,

    I'm glad to learn of your successful experiments with the UltraStable films. The fact that these (presensitized) color pigment films were made more than 15 years ago, and are still usable, illustrates another reason why dichromate
    (which would have spontaneously hardened these gelatin emulsions in less than 48 hrs) was abandoned as a sensitizing agent.

    My guess is that the stain you are seeing is a consequence of (a) washing out the exposed pigment film onto a gelatin coated paper (here, dye-transfer); (b) not clearing the print as described in the lab Manual (which unfortunately you do not have); and (c), as you said, the mordant may be playing a part (did you thoroughly wash the DT paper before using?).

    I'm pretty sure the clearing baths will not remove sensitizer stain after this much post-processing time, but if you wish to try, here's a snip from the (soon to be posted) manual relevant to that protocol:

    6. Clearing

    When all four colors have been processed and fully dried, residual
    chemicals are removed by immersing the print in Clearing Bath A for
    1 minute, followed by a brief cold water rinse and then placed in
    Clearing Bath B for an additional minute. After a final rinse, the
    print is dried and ready for finishing.

    Stock Clearing Bath A:
    Water (at 110 F) 930 ml
    Potassium Permanganate 6 g
    Sodium Chloride (Table Salt) 14 g

    Stock Clearing Bath B:
    Water (at 110 F) 940 ml
    Sodium (Meta)Bisulfite 30 g
    Sodium Sulfite 30 g

    To make working solutions of A and B, dilute each in cold water at 1:20.

  7. #37

    Join Date
    Mar 2009
    Location
    Vancouver, WA USA
    Shooter
    35mm
    Posts
    303
    Just a quick question...

    With it's (presumably) diazo sensitizer, was UltraStable intended to be used with imagesetter negatives, or could it / was it intended for use with continuous-tone negatives?

    I always thought that diazo-based sensitizers were extremely high-contrast.

    --Greg

  8. #38
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,421
    Images
    2
    Charles,

    Yes, I absolutely see why you went with diazo sensitization. It is quite remarkable honestly! By the way, do my emulsion #'s indicate a specific date, 1996?

    I think the stain must be a function of (a) mainly, as it is only in the whites of the print, and not in the area outside where the negative was. I'll try to scan it and post it for the sake of showing this. I did not wash the DT paper other than a 10' soak before sandwiching.

    Thanks much for the clearing instructions.

    Greg, from what little I've read so far, it was intended for high resolution half-tone negatives as well as cont. tone.

    Does the lab manual cover negative sensitometery? I guess time will tell!
    If you are the big tree, we are the small axe

  9. #39
    CMB
    CMB is offline

    Join Date
    Mar 2011
    Location
    Santa Cruz, CA
    Shooter
    Multi Format
    Posts
    89

    UltraStable: Sensitizers and Sensitometry

    Although some of this has been discussed here before, it bears repeating:

    1. Light hardened gelatin layers (carbon, Fresson), unlike gelatin hardened by AgX-tanning developers (carbro and dye-transfer) have a "soft" and diffuse boundary between soluble and insoluble which are sensitive to slight differences in processing . Most apparent in the highlights and in neutral color balance, these processing variations make it difficult to produce two similar continuous tone color carbon prints. Although prized by artists and hobbyists, these one-of-a-kind- print characteristics make the con-tone carbon process unsuitable for most commercial applications. Furthermore, the absence of shoulder in the (straight line) characteristic curve of carbon tissue impairs the printing of highlights (e.g. the details of a white-on-white wedding dress) necessary for accurate photographic reproduction.

    2. The UltraStable sensitizer (Diazidostilbene Sodium Sulfonate) is similar to dichromate in its ability to create a variable thickness image in response to actinic light exposure. It is also subject to the same problems of highlight loss and repeatability that affect dichromated gelatin layers. By using dot area rather than negative density (half-tone-vs-con-tone), pigment films can be processed with a high degree of repeatability and no highlight loss.

    3. UltraStable pigment films are capable of producing a four-color neutral gray scale (using screened separation negatives) with densities ranging from from .02 to 2.50+ with a base fog density of less than .01 (when printed on a white PE base). By comparison, dichromate sensitized carbon tissue, has a high base fog density (typically .10+) and when used with continuous tone separation negatives, has no visible highlight contrast until reaching a .20-.30 density level.

    4. UltraStable films are balanced so that the exposure times are the same for all four colors. Once the time to produce the recommended Cyan solid (non-screen) density of 1.39 is determined, identical exposures of the other color layers will produce Solid Densities of (approximately) M=1.34, Y=.96 and K=1.24, which, when combined, will result in a neutral (4/C) gray scale.

  10. #40
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,199
    Images
    65
    As an OTOMH guess, if those are Status D densities in paragraph #4, this indicates a relatively high level of cyan and magenta impurity in the blue region and thus somewhat unsaturated colors. The high level of K correction indicates narrow dyes at the same time. Am I correct?

    PE

Page 4 of 17 FirstFirst 1234567891014 ... LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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