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  1. #211
    Hexavalent's Avatar
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    Quote Originally Posted by analog what is that? View Post

    If you think an expensive pH meter is a necissity or a requirement for doing this..
    I don't think anybody said that. What was said is that pH "test strips" can be misleading.
    - Ian

  2. #212
    Photo Engineer's Avatar
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    I would like to add that in a dilute working solution the pH meter and test strips will be closer together, but in a concentrate they can deviate substantially due to the high salt content and its effects on pH as measured by strips.

    Also, since pH is temperature dependent and we don't know the temperature here, we can be sure that it is at least measured by the Hanna meter. There is also some compensation internally for temperature variations.

    PE

  3. #213

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    Well we now agree that the test strips and the pH meter was close in this case, so close it really didn't matter.

    We agree on temperature influernce (I already said that at the beginning), the practical solution - and that is what counts on a kitchen table budget, which is what matters here for the REST of us - it is really very simple, just let all fluids adjust themselves to the same kitchen temperature, and the difference is moot.

    I still hold it is a more pratical solution for the rst of us to order a 15$ pH meter from Hongkong and replace it as necessary.

    What was the price of that thing, did you say?

    And we should all focus on the fact that pH was double-checked here aqnd hovers around pH 8, I doubt that anyone can guarantee the value down to the last 1/10, since we wasn't there, have no idea if the meter was properly set up etc etc etc, this is not like buying a yardstick......

  4. #214

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    Quote Originally Posted by analog what is that? View Post
    Re the test strips and the pH-meter :
    Test strips 7.85 +- 0.20
    pH meter 8.05 +- 0.15

    Your test strips was definitely NOT significantly off, there is not anything in the whole world that is an EXACT measure, especially when it comes to pH measurements, electrode, exact mix, temperature.... a lot of stuff enters the equation here.

    I'd say your reasoning from the start based on the test strips was sound, and that you was in the ball park all the time.
    Yes there it was my reference to temperature to begin with.............

  5. #215

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    Checked out the Hanna meter, it is virtually the same as my Hongkong meter, included the buffers to set up and control the meter, save for one thing that I have no use for: temperature meter. Not necessary since I always store all chemistry including the fresh water needed in a termostat controlled room at 20,4 centigrade for at least 24 hrs....

    This cost 90 bux from Amazon plus shipping, mine guaranteed to the same 0,1 units did cost 15 bux from Hongkong, including postage.............

    Do your own math.

  6. #216

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    Quote Originally Posted by Alan Johnson View Post
    The formula type is new to APUG as far as I know.
    I went ahead and posted a slightly improved formula (with a higher pH) as a new thread. The name "PC-Sulfite" follows the way Gainer named his developers, and is certainly descriptive of the formula.

    Mark Overton

  7. #217

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    Quote Originally Posted by Photo Engineer View Post
    I'll bet the results make you very happy too! That is how I feel when something works out well. Enjoy.
    Yes, I am enjoying this! And certainly appreciating your assistance!

    As you can tell from my intro in the new PC-Sulfite thread, I can hardly believe that something so simple is actually new. That developer certainly is down to the bare essentials, and yet it looks as good as XTOL. Hard to believe, and yet I've got the neg's to prove it.

    Mark Overton

  8. #218
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    Well, the next thing is to work on a concentrate. Here is another hint: Kodak was working (at the end) on small packets of powdered developers, extreme concentrates, and (ta da) tablet developers similar to Alka-Seltszer. Drop into water for a single use. Makes 1 L.

    What do you think of this? They were working on a whole host of new concepts in delivery to the customer, but a failing market killed all of it off.

    PE

  9. #219

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    Quote Originally Posted by analog what is that? View Post
    If you think an expensive pH meter is a necissity or a requirement for doing this, you are doing your readers a disservice, given the state of "analog" photography, we most assuredly needs every experimenter and anyone willing to use film, to keep this thing alive.
    Well, let's examine the disservice. The disservice is that, long threads are continued to modify one thing into another, based on incomplete understanding on the nature of the technology and poor judgment. To put it into your perspective, “given the state of analog photography” what we most assuredly need are a good practical and sustainable processing system, not every amateur experimenter or bastardizer, and anyone willing to use film to actually create art or commercial art that is worthy of some audience.

    pH meter is certainly not a requirement for photographers. But if you are a chemist formulating formula and being responsible about what he or she reports, it is crucial. At the same time, measuring pH is not a trivial business. It is a lot harder than measuring voltage or complex impedance, for that matter. All pH electrodes have limitations, and photographic chemicals are one of the most tricky solutions to measure, and also just be compatible with the electrode... many people buy wrong electrode and they have no idea of the limitations of the measurements they are making. A pH meter don’t measure pH, unless you calibrate it correctly, maintain it correctly and use it correctly. Standard pH calibration buffers are to be used at 25C. But the photographic solutions are typically used at 20C. Solution pH depends on temperature and dilution, but each solution responds to these factors differently. The temperature compensation functions built into some meters only take care of the temperature dependency of the electrode, not the standard buffer solution or the test solution. (Therefore, many scientists simply do not use such function; they avoid the issue by carefully designing the experimental protocol. Industrial engineers simply incorporate these factors into the plant control programs.)

    Incidentally, 0.2 unit variation is pretty lousy for a film developer. It’s okay for print developers. If fix or wash aid, an error of 0.2 unit is insignificant.

    Also incidentally, it is true that test strips are lousy. They have good uses, in many cases adequate, but for careful experimentation of anything, it is not. Also, careful experimentation is always expensive. It is certainly not for people who puts budget before knowledge.
    Last edited by Ryuji; 12-29-2011 at 06:36 PM. Click to view previous post history.

  10. #220

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    Quote Originally Posted by Hexavalent View Post
    With the exception of $ task-specific items, pH "test-strips" are a poor choice for any truly meaningful quantitative work. The investment in a quality meter will pay for itself by providing trustworthy accurate readings.
    And anyone who is not willing to make every effort to be accurate should not call their work science or engineering.



 

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