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  1. #521

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    Quote Originally Posted by sun of sand View Post
    frame 24 appears that concentrate has slightly finer grain but xtol is still sharper. everything seems equal otherwise
    I'm not sure where frame 24 is. Could you give the posting number? It's in the upper-right corner of the posting. For example, this is posting #521.

    BTW, having XTOL last 4 years is amazing. You mention keeping it chilled: Do you have issues with precipitate collecting at the bottom of the bottle? When I tried refrigerating my XTOL, I quickly got some precipitation.

    Mark Overton

  2. #522

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    T-Max 100 -- A nice surprise

    I mentioned earlier that with 214D, T-Max 100 (TMX) has an early shoulder, so you must meter accurately at box speed. I considered that a borderline failure until I looked in the loupes. Wow! Fine grain! The grain from 214D is significantly finer than XTOL. Here are scans:

    XTOL: Click image for larger version. 

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ID:	66843 214D: Click image for larger version. 

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ID:	66844

    Grain looks equally better in loupes too. The camera was misfocussed a bit in the second image, so you can't gauge sharpness from these scans. But I examined the Mackie lines outlining the edge-markings in loupes, and sharpening looks the same with both developers.

    Films normally give you a grain-speed trade-off. But TMX gives you a grain-shoulder trade-off. With 214D, you get an early shoulder but very fine grain.

    -----

    I've decided to call this developer "Mocon". Can you guess why? Testing is done, and these are the final times (agitate once/minute for 5 seconds):

    Tri-X ................. 13.5
    T-Max 100 ........ 14 (meter accurately due to early shoulder)
    T-Max 400 ........ 13.5
    Delta 100 ......... 12.25
    Delta 400 ......... 18
    Delta 3200 ....... 25 or longer
    Pan-F+ ............. 12.25
    FP4+ ................ 16
    HP5+ ................ 15
    Acros ............... 15
    Neopan 400 ..... 14.25

    I'm writing a report which I'll post to the Articles section in apug. Any comments or requests before I call this project finished?

    Mark Overton

  3. #523

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    Mark Overton Concentrate ?

  4. #524
    Bruce Osgood's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Mark Overton Concentrate ?
    Make since to me.

  5. #525

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    Previously it was found that the similar D-316 concentrate went orange after 1 year exposure to air and Mark suggested the color could be used to estimate any needed increase in developing time.
    I made the following 3 separate solutions in deionized water and exposed each to air oxidation for 37 days:

    Sodium ascorbate 12g/L
    Phenidone 0.15g/L
    Sodium ascorbate 12g/L + Sodium sulfite 20g/L

    Attachments show that the solution containing sodium ascorbate alone went orange, strongly suggesting the orange color is due to the formation of an ascorbate oxidation product, it does not come from phenidone.
    Addition of sodium sulfite to sodium ascorbate apparently prevented the formation of the orange compound, perhaps that is why it does not show up in oxidized Xtol.

    There is some recent research on ascorbate oxidation in the human retina and also in non-enzymatic browning in foods but I did not find any mention of an orange compound so cannot say what it's name may be.
    Attached Thumbnails Attached Thumbnails Ascorbate vs Phenidone.jpg   Ascorbate vs Ascorbate+Sulfite.jpg  

  6. #526

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    @Michael - You got it right!

    @Alan - Interesting experiment. Where did you find sodium ascorbate? I couldn't find a source for it here in the states. Anyway, if you still have those fluids, it would be interesting to add some sodium sulfite to the ascorbate and phenidone solutions to see if the colour clears. I'll predict that (1) phenidone's colour will clear because the sulfite should restore the phenidone, and that (2) the orange ascorbate will not clear. The conclusion would be the same as your conclusion: The orange is due to oxidized ascorbate.

    Mark Overton

  7. #527

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    Sodium ascorbate was from ebay, it is a food supplement.
    I want to run on the experiment I described to see if the orange compound is furthur oxidized so won't add anything at the moment.

    Another experiment I ran was to dilute D-316 concentrate (no sulfite) 1+49 in deionized water and expose to air.For the first 20 days it turned slowly yellow, then during days 21-25 went orange. After 34days I added sodium sulfite 45g/L , a film leader developed in this showed very little blackening, the D-316 was pretty much all oxidized.I divided this solution into two parts and tested each with addition:

    (1)Add phenidone-produced a slightly grey film leader.I ran a blank test with phenidone/sulfite only and some boric acid to get the same pH ,this also produced a slightly grey film leader.Conclusion-the ascorbate was completely oxidized and added phenidone was not regenerated.
    (2)Add sodium ascorbate-produced a black film leader.Conclusion- some of the phenidone survived 34 days oxidation and was regenerated.

    It seems likely all the ascorbate is oxidized first , before the phenidone.

  8. #528
    Rafal Lukawiecki's Avatar
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    Quote Originally Posted by albada View Post
    Testing is done, and these are the final times[...]
    Congratulations, Mark! Next time you visit Ireland, let me know and I'd love to buy you a drink—thank you for your impressive work.
    Rafal Lukawiecki
    See rafal.net | Read rafal.net/articles

  9. #529
    PhotoJim's Avatar
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    Quote Originally Posted by albada View Post
    Where did you find sodium ascorbate? I couldn't find a source for it here in the states.
    Photographer's Formulary doesn't have it?
    Jim MacKenzie - Regina, Saskatchewan, Canada

    A bunch of Nikons; Feds, Zorkis and a Kiev; Pentax 67-II (inherited from my deceased father-in-law); Bronica SQ-A; and a nice Shen Hao 4x5 field camera with 3 decent lenses that needs to be taken outside more. Oh, and as of mid-2012, one of those bodies we don't talk about here.

    Favourite film: do I need to pick only one?

  10. #530

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    They have ascorbic acid, not the salt.



 

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