Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,860   Posts: 1,583,162   Online: 712
      
Page 24 of 58 FirstFirst ... 141819202122232425262728293034 ... LastLast
Results 231 to 240 of 576
  1. #231
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,540
    Images
    65
    Thanks Mark;

    IMHO the experimental developer looks less sharp. Look at the numbers on the lens in both crops. The grain is similar and low.

    PE

  2. #232

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    674
    Quote Originally Posted by Photo Engineer View Post
    Thanks Mark;
    IMHO the experimental developer looks less sharp. Look at the numbers on the lens in both crops. The grain is similar and low.
    PE
    Oops, that was poor scanner-focus, being near the edge of the neg-carrier.
    I re-scanned that neg, but this time manually focusing the scanner on that crop-area. That made the scan sharper there:

    Click image for larger version. 

Name:	3-18-Concen1stCrop.jpg 
Views:	31 
Size:	123.9 KB 
ID:	43622

    Mark Overton

  3. #233
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,540
    Images
    65
    Thanks again. Looks better now. There is some "hash" on the right top in the dense areas.

    Both developers look similar in contrast to me when viewed as thumbnails. I can't view them side-by-side for a more accurate examination. Just keep on working. looks interesting and you are learning as you go.

    PE

  4. #234

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    674
    Here's a failure I'd like some advice about.

    Moving toward creating a concentrate, I modified the PC-Sulfite formula by replacing the sodium sulfite with TEA. The big difference between this and PC-TEA is the pH is much lower, and thus there's more AA and phenidone per liter to keep the dev-time at 7-8 minutes. Here's the 1-liter test-formula:

    TEA ................. 5 ml
    Ascorbic acid ... 2.7 g
    Phenidone ....... 0.18 g
    pH = 8.3
    The AA and phenidone are about the same as PC-Sulfite, and the pH is the same. So I expected the dev-times to be the same. But 7.5 min at 20C produced a very thin test-strip. A second strip at 9.5 minutes was also thin, plus the developer had turned light yellow. Adding a little more ascorbic acid made it clear again.

    I even tried quadrupling the TEA and AA (keeping the pH at 8.3), and an 8 minute time gave negatives that were a little thin, and yellowish developer again. It seems that the developer is quickly becoming exhausted or oxidized.

    Any idea why?

    I know that sulfite is an antioxidant, but ascorbic acid is an even stronger antioxidant, so I'm surprised that swapping out the sulfite caused this.
    Further mysterious is the fact that PC-TEA does not exhibit this problem, and it has even less AA and phenidone per liter than my formula above. However, PC-TEA operates at a high pH around 10, and I'll speculate that that high pH is activating the phenidone in PC-TEA rather than the AA. But that's just my speculation...

    Mark Overton

  5. #235
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,540
    Images
    65
    Mark;

    Perhaps you have missed the buffer capacity of the Sulfite compared to TEA among other things, and that involves the molecular weights as well. Look at the moles per liter of TEA and Na2SO3.

    PE

  6. #236

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    674
    Quote Originally Posted by Photo Engineer View Post
    Perhaps you have missed the buffer capacity of the Sulfite compared to TEA among other things, and that involves the molecular weights as well. Look at the moles per liter of TEA and Na2SO3.
    I forgot to mention: The pH was the same after development as it was before (8.3). I checked this on the second run wondering the if pH had plunged. I even checked pH once a minute while developing a leader -- always at 8.3. So I don't think poor buffering is the culprit.

    Sulfite and TEA have similar molecular weights: 126 vs 149. So even after quadrupling, I was putting far fewer moles/liter in there. But given that pH is constant, I don't know what harm fewer moles of alkali would do.

    Mark Overton

  7. #237
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,540
    Images
    65
    Mark;

    The pH does not give one the buffer capacity. They are not the same. One refers to the inertia of the movement of the pH with any addition of acid and the other refers to just an absolute number of Hydrogen or Hydroxyl ions present. So, Na2SO3, if it ionizes more fully than TEA even at the same weight, will probably buffer better. That is poorly stated but gives a gist of the situation.

    Since SO3-- puts more Ag+ into solution being a mild solvent, a mix of DEA/MEA/TEA might simulate SO3--. IDK. Try it. I have my own solutions to this problem.

    PE

  8. #238

    Join Date
    Nov 2004
    Posts
    1,178
    Quote Originally Posted by albada View Post
    Here's a failure I'd like some advice about.

    Moving toward creating a concentrate, I modified the PC-Sulfite formula by replacing the sodium sulfite with TEA. The big difference between this and PC-TEA is the pH is much lower, and thus there's more AA and phenidone per liter to keep the dev-time at 7-8 minutes. Here's the 1-liter test-formula:

    TEA ................. 5 ml
    Ascorbic acid ... 2.7 g
    Phenidone ....... 0.18 g
    pH = 8.3
    The AA and phenidone are about the same as PC-Sulfite, and the pH is the same. So I expected the dev-times to be the same. But 7.5 min at 20C produced a very thin test-strip. A second strip at 9.5 minutes was also thin, plus the developer had turned light yellow. Adding a little more ascorbic acid made it clear again.


    Mark Overton
    I made up this solution in tap water and measured its pH.
    I get pH= 8.0 with an inexpensive pen type meter,but it calibrates accurately vs 2 buffers.
    btw there are 2 types of TEA, 97% and 99% and they have different pH. I used 97%.
    So partly pH may be a factor in your result. Also, not mentioned, sulfite is known to dissolve some silver halide and uncover latent image centers which TEA may not do and this may be a factor as well.

  9. #239

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    674
    Quote Originally Posted by Alan Johnson View Post
    I get pH= 8.0
    This pH-difference might be due to measurement-variations. I mix 200 ml test-solutions, and divide the formula by 5. For this, that means 1 ml of TEA and about 1/2 gram of AA. The 1 ml of TEA makes the pH swing a long distance, from 3.0 to 8.3. That's a range of 8.3-3 = 5.3. A shift of 0.3 represents a 6% shift over that range. For small liquid quantities, I use a syringe with a 3 ml capacity, and which is graduated in 0.1 ml increments. I can probably get within 0.05 ml with it. That's a 5% random variation in my measurement right there. So your 8.0 versus my 8.3 is probably due to measurement-variation.

    Did you try a clip test with this formula? Even 10 minutes at 21C gave me a thin clip.

    Mark Overton

  10. #240
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,822
    Images
    10
    Mark,

    could you find out whether that clip ever turns normal if you dev long enough? PE suggested in some previous post that at EK they investigated slow developer for extra fine grain. Since your pH seems to linger around the lowest possible value for B&W dev (according to what Ryuji posted), you may have inadvertently walked the path Ron suggested.

    About your pH measurements: nobody expects your whole liquid to change pH from the couple of silver grains reacting with your dev, but locally the pH could change thereby reducing contrast (similar to stand development). The easiest way for you to find out is by changing agitation: if strong agitation creates much thicker negs, some local effect may be the culprit and buffering could help.

    If your test clip turns normal after much longer dev, it would be interesting to see results, especially with regard to grain. On the one side you achieved extra slow development, on the other side you omitted Na2SO3 which acts as a grain solvent.
    Trying to be the best of whatever I am, even if what I am is no good.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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