Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,698   Posts: 1,482,558   Online: 888
      
Page 32 of 55 FirstFirst ... 222627282930313233343536373842 ... LastLast
Results 311 to 320 of 550
  1. #311

    Join Date
    Nov 2004
    Posts
    1,091
    In post 302 the formula has 2.7g metaborate so if 2.4 g crystallised I cannot figure out if post 302 formula would be OK.

  2. #312

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    646
    Quote Originally Posted by Alan Johnson View Post
    In post 302 the formula has 2.7g metaborate so if 2.4 g crystallised I cannot figure out if post 302 formula would be OK.
    Post 302 crystallizes also. I ran strips with that baseline developer by mixing directly into water, but when I mixed it as a concentrate five days ago, it crystallized. Then I created more concentrates of various formulations, made a table of all concentrates I've ever mixed since January, and looked for patterns in the numbers. The result is yesterday's long posting, and the realization that D316 happened to hit the narrow usable window.

    Mark Overton

  3. #313

    Join Date
    Nov 2004
    Posts
    1,091
    I belive the sodium metaborate that Silverprint sell in the UK is the 8-mol aka Kodalk.This has more water in it and should be less prone to crystallisation than the 4-mol from the Formulary.
    There is so much ascorbate in the concentrate it may still be resistant to aerial oxidation.

  4. #314

    Join Date
    Nov 2002
    Location
    Melbourne, Australia
    Shooter
    Medium Format
    Posts
    949
    Quote Originally Posted by Alan Johnson View Post
    I belive the sodium metaborate that Silverprint sell in the UK is the 8-mol aka Kodalk.This has more water in it and should be less prone to crystallisation than the 4-mol from the Formulary.
    There is so much ascorbate in the concentrate it may still be resistant to aerial oxidation.
    The hydration of sodium metaborate is confusing. Here is a bit of information that I copied from the long-lamented Ryuji Suzuki website in relation to this nomenclature. I hope it is helpful.

    <start quote>


    Hydration of sodium metaborate, NaBO2, and that of Kodalk

    Kodalk or "Kodak balanced alkali" is Eastman Kodak Company's trade name for sodium metaborate. The largest supplier and research institution for this compound is U.S. Borax Research Corp. in Anaheim, California. In Ullmann's Encyclopedia of Industrial Chemistry, Robert A. Smith of U.S. Borax explains industrial production processes for this compound among other boron compounds in detail.

    In old literature, sodium metaborate tetrahydrate (CAS 10555-76-7) is denoted Na2B2O4 - 8H2O. This lead to old nomenclature describing hydration of sodium metaborate to be octahydrate. However, as more modern techniques became available, the actual structure of sodium metaborate is known to be better described by NaB(OH)4 - 2H2O, and this substance became to be commonly denoted by NaBO2 - 4H2O, hence tetrahydrate. According to detailed catalogues of several laboratories chemical suppliers, there is no NaBO2 - 8H2O commonly traded today. Robert Smith of U.S. Borax explains that "sodium metaborate tetrahydrate is the stable solid phase in contact with its saturated solution between 11.5 and 53.6°C." Therefore, octahydrate in old nomenclature and tetrahydrate in modern nomenclature indicate the identical chemical in the same hydration form. It is just that the nominal formula weight for tetrahydrate is half that of octahydrate. One mole of tetrahydrate would provide one mole of B(OH)4- in aqueous solution, while octahydrate would provide two moles.

    The formula weight for this sodium metaborate tetrahydrate is 137.8. Common procedures for making sodium metaborate from borax and sodium hydroxide are often based on incorrect assumption that Kodalk is actually NaBO2 - 8H2O, and they have to be corrected. Fortunatelly, the proportion of mixture is correct, and the error is in final dilution, so solutions made from incorrect instruction can still be used, but by increased amount.

    In order to make 1.0g sodium metaborate tetrahydrate, mix 0.692g borax and 0.145g sodium hydroxide. When dissolved in water, these two make solutions of identical composition.

    <end quote>

  5. #315

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    646
    Thanks for the postings about sodium metaborate. I was unaware of the history of the "4-mol" and "8-mol" notations; I only knew they are confusing. In the concentrate, I wonder if the degree of hydration makes any difference. That is, I suspect the water is driven out by heat, and if so, the initial hydration makes no difference (except when weighing the powder). It would be easy to experimentally determine if the water is driven out -- maybe I'll do that.

    Also, my long posting gives the impression that there's almost no flexibility of quantities of chemicals. That isn't so. If you're willing to decrease the concentration-ratio (i.e., use more PG in relation to the powders), then solubilities are less of an issue, giving you a wider range of feasible quantities.

    Today, I ran a test-strip using the D316 concentrate:
    pH is 8.08.
    13:45 minutes (at 20C) with TMY-2.
    Density-curve is very close to XTOL.
    Grain and sharpness both match XTOL when compared with my loupes.

    The specific gravity of my batch of D316 is 1.146. If you have a scale, measure out 23 grams/L because weighing is more accurate than measuring small volumes with a graduate.

    I've found that in D316's formula, you can change the sodium metaborate (4 mol) from 2.0 g/L up to 2.7 g/L, and all will give you excellent developers (mixed directly into water; no concentrate). I was hoping to hit a pH near XTOL's 8.20, because the dev-times of various films would probably be closer to some constant (about 1.9) multiplied by XTOL's time. D316's pH of 8.08 means that constant may vary more from film to film. That's a minor problem. Anyway, I'll try raising pH by boosting the sodium sulfite some and see how that turns out.

    Mark Overton

  6. #316

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    646
    Those of you who run test-strips may find this holder useful. Anyone can make it, and it closely mimics the environment of a roll of film. In particular, it eliminates the problem of developer-currents causing uneven (or extra) development in the strips.

    Click image for larger version. 

Name:	StripHolder2.jpg 
Views:	43 
Size:	123.0 KB 
ID:	59762

    Using a hacksaw, I cut a PVC pipe fitting in half, and cut two interior slots in which the strip slides.

    Click image for larger version. 

Name:	StripHolder1.jpg 
Views:	36 
Size:	137.9 KB 
ID:	59763

    When in the tank, the emulsion faces down, so there's a narrow space between emulsion and tank-bottom, similar to the small gap between layers on a reel. As a result, the strip develops similarly to a roll. The crosspiece that's epoxied to the top prevents this strip-holder from turning upside-down during agitation.

    Click image for larger version. 

Name:	Curve12.4-XTOL.jpg 
Views:	36 
Size:	48.2 KB 
ID:	59764

    I exposed a 21-step Stouffer wedge twice, first with low exposure to show the toe, and again with high exposure to show the shoulder. The bump at X=3.0 is where the two graphs were stitched together.
    You might have noticed in the first photo that there are two frames on the strip. On the roll, I made low/high exposures in alternation, so each test-strip has both, showing everything the developer is doing, from toe to shoulder.

    This device is an improvement over the baffles I've been using. Comments, questions or suggestions?

    Mark Overton

    EDIT: I'm using a one-reel tank. It's so short that, with the crosspiece, there's not enough vertical space for the PVC strip-holder to turn upside-down, so agitation by inversion works well.
    Last edited by albada; 11-15-2012 at 05:00 PM. Click to view previous post history.

  7. #317
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,710
    Images
    65
    Very nice Mark.

    PE

  8. #318

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    646
    Quote Originally Posted by Photo Engineer View Post
    Very nice Mark.
    PE
    Ron, thanks for the encouragement. I missed Gainer and crowd by a few years, making me sometimes feel like the party is over.

    Well, here's a device I made to accurately measure strips of film, and cut them on frame-boundaries. You can use it to measure any length, including individual frames, but I'm using it to measure two-frame strips for the PVC strip-holder I posted a couple days ago.

    When shooting the roll, first mark the frame-boundary on the leader with a felt-tip marker. When rewinding, leave the leader out, and cut it on the marked frame-boundary. With the lights on, load it into the home-made frame-advancer thusly:

    Click image for larger version. 

Name:	Framer1.jpg 
Views:	33 
Size:	131.2 KB 
ID:	59866

    Position the film-edge to where the scissors will be. Load it such that the crank will be pointing down when the film is at the cut-position (as shown). Turn the darkroom-lights off (or put it into a changing-bag), and make the cuts. Because there's no drift in position, every cut will be between frames. I prefer to keep the crank in the rear, as it's out of the way when I'm handling scissors with the other hand, like this:

    Click image for larger version. 

Name:	Framer2.jpg 
Views:	32 
Size:	123.5 KB 
ID:	59867

    A couple more shots to show the construction:

    Click image for larger version. 

Name:	Framer3.jpg 
Views:	32 
Size:	112.0 KB 
ID:	59868 Click image for larger version. 

Name:	Framer4.jpg 
Views:	29 
Size:	163.3 KB 
ID:	59869

    When selecting a junk camera from which to extract a sprocket, make sure the sprocket has eight teeth, so that one revolution will be one frame. Most have eight, but a few don't. When drilling the holes, I positioned the sprocket slightly too low, so the film jammed on entry. Sanding the top of the block down a little fixed that. The slots on top of the wooden block were cut with a saw, but it took two adjacent cuts to make each slot wide enough.

    It took me an evening to make this device, but I think it was time well-spent.

    Mark Overton

  9. #319
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,710
    Images
    65
    Again Mark, very neat and useful work.

    Thanks.

    PE

  10. #320

    Join Date
    Mar 2011
    Shooter
    35mm
    Posts
    655
    Quote Originally Posted by albada View Post
    Comments, questions or suggestions?

    Mark Overton
    Mark,

    As someone with an intimate knowledge of the miracle that is the drywall screw, and 400 feet of Eastman 5222 in the freezer, I intend to slavishly copy your film winder/counter in some fashion.

    Thanks!
    s-a
    I photograph things to see what things look like photographed.
    - Garry Winogrand



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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