Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,527   Posts: 1,572,386   Online: 1140
      
Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15
  1. #11
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    849
    I have never regretted not resisting temptation. Where's the fun in that? Life is short. Play with silver.

  2. #12

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    Quote Originally Posted by Jerevan View Post
    Is the silver content related to what other chemicals there is in the emulsion, i.e can I get away with less silver using something else that is active in the emulsion and still get the same results?
    Possibly. One major role of excess silver in printing out processes is that it is used as a halogen acceptor. If you can find another suitable agent for this role (besides addition of alpha-hydroxy polycarboxylic acids that are commonly used anyway), I think there is good chance that it can be done. However, there is little modern research on this kind of stuff for printing out materials.

    A standard (old technology such as say, Tri-X) film has, as far as I get it, a silver content of 1,5g per square meter. The same content of silver could also coat the same amount of paper. I am not sure of the Ag content of T-grain films but I believe it is lower due to some manufacturing differences.
    Tri-X has more than that. 1.5g per square meter is more like for modern microfilms, copy films, lith films, etc. and modern printing papers.

    What I am really trying to figure is this idea of "silver-rich" materials. Let's say one makes a film with 3g silver per square meter. Apart from the obvious rise in costs, does it make any sense altering the levels of silver - and is there any limit to how much you can use in an emulsion?
    First of all, there are lots of films that use 3g or more. But in light of post-1950 emulsion technology (it doesn't have to be state-of-the-art or anything) silver content is merely a marketing hype that is used by some authors and retailers these days. And I don't even think the authors or retailers know the actual silver content of the materials they are talking about. Plus, older emulsions contain a lot of crystals that are not even sensitive enough and they just consumed silver and processing capacity of the chemicals. So, even if a product is indeed silver-rich, it just means technology-poor.

    You can put more silver in the emulsion if you want. But only the crystals near the surface get exposed and the bottom ones won't even get exposed enough. Also, if you put too many crystals, they increase light scattering and decrease resolution. Modern tabular grain technology and double layer coating allow a much better tradeoff of these competing factors.

    In paper emulsions, the resolution is inherently low and also irrelevant, so you can add more silver with relatively little harm but it is still unwise for the same reasons.

  3. #13
    Jerevan's Avatar
    Join Date
    Nov 2004
    Location
    Sweden
    Shooter
    35mm
    Posts
    1,871
    Images
    9
    Quote Originally Posted by dwross View Post
    I have never regretted not resisting temptation. Where's the fun in that? Life is short. Play with silver.
    True: I can resist anything but temptation, as Oscar Wilde wrote. I just need to get down to buying a balance to measure things with and I'll be making some basic emulsion in the near future.

    Ryuji,
    thanks for the information on the silver content. A few more pieces to the puzzle...
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  4. #14
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    849
    Jerevan: Excellent. You'll have a great time! Winter is a wonderful time to have an intellectual and artistic puzzle to play with. Right now, a Pacific storm is beating again my windows, and I get to go into a warm, dry, cozy darkroom. Nirvana. Best of luck to you.

  5. #15
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,384
    Images
    65
    Jerevan;

    I hope you enjoy your winter making emulsions and I wish you success.

    It is true, as I have posted before here on APUG and PN that silver rich is a myth. It is not needed to get good quality. But, the myth arose because the old silver rich films had very good quality. We see that in the nostalgia over some of the older products such as Super XX. Even today, some manufacturers advertize silver rich products which have good quality.

    We, working at home, cannot easily make double coated film or make t-grain emulsions. They are much more complex than simpler emulsion from this earlier era and the earlier emulsions, while 'silver rich' also can be 'image rich' if I may coin a term here.

    Denise has commented on how rich the blacks look in her hand coatings from the Azo type emulsion formula that she is making. This coating is silver rich but is also beautiful to behold. A typical coating contains about 250 mg/square foot or about 1.9 grams per square meter. You typically coat 12 ml per square foot or about 100 ml / square meter. (These will not match exactly as I'm doing the conversion in my head here between English and Metric but that is ball park. I hope I didn't slip a decimal.)

    That is about double the level of silver current enlarging paper level, but it works and give such a nice look I just could not resist the result myself. I could lower the silver content with appropriate addenda, but chose not to due to the appearance. This particular formula is also slightly softer in the toe than the Azo formulation and therefore gives better detail in the highlights with less need for dodging.

    The matte blacks look like black velvet.

    PE

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