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  1. #1
    Ian Grant's Avatar
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    Modern Rodinal Substitutes Part II

    Apologies for having to start a new thread but I can't read or even access the first to reply to posts.

    So with a bit of telepathy

    Quote Originally Posted by Kirk Keyes View Post
    Well, there's a problem there, as it's really hard to measure pH accurately when it gets much above 12.5 or so. You have to start getting special electrodes and the like.

    But for MSDS work, it doesn't have to be too precise.
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    Kirk

    A point that's being missed is that A&O give a figure of 2.7% Potassium Hydroxide not 3% in older Agfa MSDS.

    The pH is around 14 sure, but the actual requirement is the pH of the working dilute solution rather than the concentrate which is given elsewhere as pH 11.55, which I commented on in the first post of the thread.

    Way back Ron (PE) mentioned adjustments to Rodinal before bottling, the question we need to ask is are they adjusting on the basis of the concentrate, or also doing some tests on a dilute sample, as this will be a far more accurate indicator.

    Can someone please post a link to this continuation on the original post.

    Ian

  2. #211

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    Quote Originally Posted by Photo Engineer View Post
    I explained and posted a graph regarding Isoelectric Point with regard to gelatins some time back.

    PE
    Yea,
    I was just wondering if Kirk had something specfic in mind.

  3. #212

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    Quote Originally Posted by Ray Rogers View Post
    That is, can you give some real world examples so we can learn something?
    (I agree with the concept... but I don't have the skills just now to apply them to developers) can you show us what you mean with a practical example?
    I wasn't trying to imply anything specific to developers per se, but any chemical with both base and acid functionality on the same molecule in general. Things get more complicated with these kinds of chemicals. It can answer how they will ionize (and perhaps dissolve/not dissolve) based on the pH of the solution.
    Last edited by Kirk Keyes; 09-18-2009 at 03:20 PM. Click to view previous post history.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  4. #213

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    Quote Originally Posted by Kirk Keyes View Post
    I wasn't trying to imply anything specific to developers per se, but any chemical with both base and acid functionality on the same molecule in general....
    Understood...

    Thanks Kirk

  5. #214
    gainer's Avatar
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    1. Take 500 ml water. Add 1 gram p-aminophenol base. Load the developing tank and be ready to pour before adding 5.2 ml of a 10% KOH solution. The solution will turn very dark very soon after the KOH is added and stirred in. Developing time for HP5+ at 70 F is 18 minutes.

    2. Repeat the above but add 15 to 20 ml of the 45% K3SO3 solution before adding the KOH. Developing time for HP5+ is now 9 minutes. This is not due to difference in pH but to the anyioxidant effect of the sulfite.

    The attachments show that overall grain and acutance are not observably different with or without sulfite. The scans are from real photographic prints. I copied out the detail pictures before reducing the file size of the overall pictures so one should be able to see the detail in "The Silver Chalice." Also, there is an aluminum-framed window screen standing behind the armchair that makes a good measure of resolution. The virtue of adding a lot of sulfite to the stock solution will be mostly in preservation. Even the 384 grams/liter proposed by Ian produces only about 7.5 grams/liter in the working solution at 1+50 dilution.

    I have not yet tried adding bromide or EDTA.
    Attached Thumbnails Attached Thumbnails PAP+KOH NOSULFITE.jpg   PAP+KOH+noSulfite detail.jpg   PAP+KOH+SULFITE detail.jpg  
    Gadget Gainer

  6. #215
    Photo Engineer's Avatar
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    There is a substantial difference between 2 and 3 Patrick.

    PE

  7. #216
    gainer's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    There is a substantial difference between 2 and 3 Patrick.

    PE
    What differencr caught your eye?
    Gadget Gainer

  8. #217
    gainer's Avatar
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    Let's do it this way. You tell me which of these had the sulfite. And if it seems vry obvious to you, remember that these are, if you view or print them to 10" height, 32 X magnifications of 35 mm HP5+ frames. Also, I intend to do other values of sulfite between 0 and 380 grams per liter to see if there's a break point at which the developer activity takes a jump.
    Attached Thumbnails Attached Thumbnails Rod Test C.jpg   Rod Test D.jpg  
    Gadget Gainer

  9. #218
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    After reading almost all 40 pages on this topic, I've learned a lot about Rodinal (my favorite developer, especially with rollei retro 100 of which I have lots).

    Gainer, the left two crops in your last post look better to me (and picture nr 3 in your previous post). Seems like quite a bit of difference to me?!

  10. #219
    Photo Engineer's Avatar
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    Patrick, I am just commenting on the differences. The left of the two is higher in contrast or slightly lighter in the highlight areas and the one on the right is darker and lower in contrast. That makes comparison, for me, more difficult.

    PE

  11. #220
    gainer's Avatar
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    There is an artifice that will occur in periodic sampling such as digitizing when the original signal has frequency higher than the sampling frequency. The higher frequencies are folded back to the low end. The effect in a photograph with any amount of grain can make the grain look coarser than it would when viewing the photo directly. I was a bit sloppy in the post with the three images in that I did not get the same number of pixels per centimeter in both detail crops. I resampled the detail croppings at 2400 PPI for the most recent post. These are the same two negatives.
    Gadget Gainer



 

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