Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,054   Posts: 1,561,287   Online: 1219
      
Page 3 of 58 FirstFirst 1234567891353 ... LastLast
Results 21 to 30 of 576
  1. #21

    Join Date
    Nov 2004
    Posts
    1,163
    Some comments from Ryuji Suzuki on the effects of salicylic acid and TEA in this thread:
    http://www.apug.org/forums/archive/i...p/t-47390.html
    I believe only the print developer ever went into production.It is more exposed to oxidation and the effects of the iron and copper likely more than they would be with the low pH DS-10.
    I suggest recalculate your formula with about 1g/L salicylic acid.IIRC from making DS-12, that much dissolves OK.

  2. #22
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,265
    Images
    65
    The Sulfite is going to either be a superb silver halide solvent or a superb pseudo alkali, but not really both in this formula. It needs something else IMHO and Ryuji seems to have worked out what is best for these ingredients. I'm not saying that your idea won't work, just that it may be quite different than you expect in both activity and pH, and that you may have to tinker with it a bit.

    Let us know how the pH turns out.

    PE

  3. #23

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    671
    Quote Originally Posted by Alan Johnson View Post
    Some comments from Ryuji Suzuki on the effects of salicylic acid and TEA in this thread:
    http://www.apug.org/forums/archive/i...p/t-47390.html
    I believe only the print developer ever went into production.It is more exposed to oxidation and the effects of the iron and copper likely more than they would be with the low pH DS-10.
    I suggest recalculate your formula with about 1g/L salicylic acid.IIRC from making DS-12, that much dissolves OK.
    Thanks for the link with Ryuji's rationale for the TEA and salicylic acid. Here are some telling fragments:
    "the main purpose of TEA in DS-14 is iron and copper chelator"
    "The quantities of TEA and salicylic acid are rather small, but you'll see improved keeping properties"
    Based on his posting, TEA and salicylic acid are solely for chelation and scavenging radicals -- both to improve storage. I'm thinking that for a mix-as-you-use developer, dropping both of these may be safe.

    Quote Originally Posted by PE View Post
    The Sulfite is going to either be a superb silver halide solvent or a superb pseudo alkali, but not really both in this formula
    This is interesting, and I guess we can only find out by trying. Easy enough once the chems arrive. No email-confirmation from Photo Formulary today; did they take today off?

    I remember reading a posting somewhere that tests showed that having too much ascorbate (ascorbic acid?) in a developer is harmless. If so, we can add extra to drop the pH to 8.0. That means we can also delete the boric acid, resulting in this simple formula:

    Water ................................... 750 ml
    Phenidone ............................ 0.15 g developer
    Ascorbic Acid ....................... 14.3 g developer, and adjust pH to 8.00
    Sodium Sulfite (anhydrous) .... 75 g alkali and halide-solvent
    Water to make ...................... 1 L
    I note that this formula is similar to Instant Mytol (by Jordan; see http://www.photosensitive.ca/wp/easy-film-developers)
    11.5 g ascorbic acid (same molar concentration of ascorbate as MYTOL)
    0.15 g phenidone
    60 g sodium sulfite (anhydrous)
    13.4 ml triethanolamine or 7 g sodium metaborate (“Kodalk”)

    All this looks nice on paper, but I don't trust my pH-calculations, and PE's warnings about surprises with pH and activity are going to be on my mind...

    Mark Overton

  4. #24
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,265
    Images
    65
    You must remember that there are tread off situations. The developers at Kodak cost millions of dollars to develop. All others were done on a shoestring by comparison.

    As for chelating ability of TEA, well in order of ability, you may want to look at NTA http://chemicalland21.com/specialtyc...g%20agents.htm for information. NTA is the fully oxidized form of TEA and is a superb chelating agent used in Kodak C41 bleach 3. TEA by comparison is a pale equivalent that just barely qualifies as a chelating agent.

    PE

  5. #25

    Join Date
    Nov 2004
    Posts
    1,163
    The interesting question has been raised "why bother to buffer?"
    For each atom of metallic silver formed a hydrogen ion is produced which will lower the pH at the grain surface and slow development.The effect of this I do not know.

  6. #26
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,265
    Images
    65
    Lowering of pH due to lack of buffer capacity can lower contrast overall, lower Dmax, or increase edge effects in borders between objects of different density.

    It depends on film and developer composition.

    PE

  7. #27

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,901
    In the presence of a relatively high amount of sulfite the low activity would also tend to decrease sharpness/reduce graininess, wouldn't it?

    I don't know, as a substitute for XTOL, this home brew formula seems inferior in all respects.

  8. #28
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,265
    Images
    65
    Sulfite at this level tends to act as a mile silver halide solvent much as it does in D-76. As we all know, it is also a stabilizer (antioxidant) and a mild alkali or a weak base.

    PE

  9. #29

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,901
    But if the pH, and therefore activity is low enough the film spends a significantly longer amount of time in contact with the sulfite. I'm thinking here of how D25 works compared to D23, although they both have more sulfite and don't use phenidone.

    Am I wrong in thinking the formula:

    Water ................................... 750 ml
    Phenidone ............................ 0.15 g developer
    Ascorbic Acid ....................... 14.3 g developer, and adjust pH to 8.00
    Sodium Sulfite (anhydrous) .... 75 g alkali and halide-solvent
    Water to make ...................... 1 L

    ...would be a very low energy developer? This seems almost like a POTA variant with lower pH.

  10. #30
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,265
    Images
    65
    It looks like D-76 with the HQ and Metol replaced by the Phenidone and AA. IDK. There is no great synergy between P and AA but there is between Metol and HQ which is what makes it work. Try it. I suspect again it will depend on film and will need some tinkering. These things always do.

    We went through many variants for TF-5 and Liquidol to come up with final formulas that performed as they now do.

    PE

Page 3 of 58 FirstFirst 1234567891353 ... LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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