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  1. #281

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    Copper sulfate would be a good choice. It's cheap and readily available. The common name is blue stone
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  2. #282

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    In the UK the maximum limit for copper in drinking water is 2mg/L and for iron 0.2mg/L.I don't know the US values.
    http://dwi.defra.gov.uk/about/annual...ir09thames.pdf
    I daresay there may be high copper concentations in the UK which has mostly copper pipes and high iron concentrations in the US (which has mainly iron pipes?).

  3. #283
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    Quote Originally Posted by Alan Johnson View Post
    In the UK the maximum limit for copper in drinking water is 2mg/L and for iron 0.2mg/L.I don't know the US values.
    And what are the maximum limits of copper and iron impurities in the sodium sulfite used for mixing photochemistry?
    Trying to be the best of whatever I am, even if what I am is no good.

  4. #284

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    Quote Originally Posted by Alan Johnson View Post
    In the UK the maximum limit for copper in drinking water is 2mg/L and for iron 0.2mg/L.I don't know the US values.
    http://dwi.defra.gov.uk/about/annual...ir09thames.pdf
    I daresay there may be high copper concentations in the UK which has mostly copper pipes and high iron concentrations in the US (which has mainly iron pipes?).
    Alan, thanks for the info. I'll use your copper value of 2mg/L.

    Regarding iron (and as Rudi hinted at above), it seems that more iron comes from impurities in the sodium sulfite than from tap-water. Spectrum Chemical's grades of sodium sulfite contain up to .001% iron, and their sodium metabisulfite contain up to .002% iron. In my developer, that's 0.9mg from the 45g of sulfite. I'll suppose I'll add 1mg of iron and 2mg of copper. Does anyone have more data about iron-content of sodium sulfite?

    BTW, I did a leader-test last night from the baseline dev that had sat for 24 hours. Density was 2.6, whereas I would expect around 2.9. That tells me the Fenton reaction isn't overly fast using my chemicals in distilled water.

    Mark Overton

  5. #285

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    I haven't yet received my chemicals that will let me deliberately put Cu and Fe contaminants into the developer, but I did some tests to see how it currently holds up over 24-hours. I mixed the baseline developer in distilled water, with and without salicylic acid, and did leader tests when mixed, and after 24 hours. Here are the leader densities:

    No salicylic, when mixed: 3.62
    No salicylic, after 24 hrs: 3.65 (no loss)

    With salicylic, when mixed: 3.67
    With salicylic, after 24 hrs: 3.57 (small loss)

    So salicylic acid made longevity worse? Huh?

    Anyway, this shows that my chemicals (especially sulfite) are low enough in Cu and Fe that there's little or no perceptible loss of quality after one day. Maybe I should try this with our hard tap-water.

    Mark Overton

  6. #286

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    Interesting result: When developing a complete roll, you would expect a developer to develop less (make thinner neg's) than with a test-strip. That's because with a whole roll, there's much less developer present per square cm of film, so it gets more exhausted. So why did this happen with the baseline developer?:

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    With the roll, the developer became more active! It overdeveloped the roll, using the same time and temperature (and same pH). I'll guess that the by-products of the phenidone and AA accelerate development. I remember reading about this, but this is the first time I've seen it. I'll reduce development-time a little, unless somebody has a different idea...

    Mark Overton

  7. #287

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    Quote Originally Posted by albada View Post
    Regarding iron (and as Rudi hinted at above), it seems that more iron comes from impurities in the sodium sulfite than from tap-water. Spectrum Chemical's grades of sodium sulfite contain up to .001% iron, and their sodium metabisulfite contain up to .002% iron. In my developer, that's 0.9mg from the 45g of sulfite. I'll suppose I'll add 1mg of iron and 2mg of copper. Does anyone have more data about iron-content of sodium sulfite?
    Hi Mark, I no longer have any standards for photograde chemicals. At one time I did, and once or twice posted some data as examples. One I can still find is for potassium carbonate - not your chemical - but probably similar specs. This was from ANSI PH4.229-1987: Iron (Fe): 0.001% (m/m) max. So my guess is that the sulfite spec was the same, meaning that probably your supplier (Spectrum) meets a photograde spec for iron in sulfite. Probably. (Assuming carbonate and sulfite had the same spec for iron, and that the standard hasn't changed, and that I didn't mistype the original post.)

    Regarding water, in general, my standard photo reference has always been a 1965 paper, Water Quality Criteria, by Lloyd West of Kodak. (The 1997 edition of IS&T's Handbook of Photographic Science and Engineering still used this paper as a reference.) Per West, in 1965 the US Drinking Water Standard was 0.3 ppm iron. He notes, "that level of iron can be expected to gradually produce stains and deposits on equipment and possibly photographic products." In a separate table of "Practical Limits for Common Impurities for Water," he lists 0.1 ppm for each of copper, iron, and manganese.

    West only has a couple of paragraphs on iron, also saying "Iron is usually present in well water...especially in acid waters of pH less than 7. Sulfates of iron and aluminum are common sources of acidity of well waters."

    Part of what West did was a survey of processing labs, and specs on their water. Today, you can likely find all of those water analyses on-line, searching for the city name and "water analysis," or "water quality report."

    Hope this helps a bit.

  8. #288
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    Quote Originally Posted by albada View Post
    I'll guess that the by-products of the phenidone and AA accelerate development. I remember reading about this, but this is the first time I've seen it. I'll reduce development-time a little, unless somebody has a different idea...
    Is there a chance that the oxidation products of Ascorbic Acid are not acidic and that the pH rises as more silver gets developed? This could at some point cause some AA to develop on its own, especially in the regions which have already seen some development (Silver == catalyst), and the curve would look like the one you got.

    A pH measurement before and after development and comparing these for test clip and whole roll would likely shed some insight. You could also test if consecutive test clips souped with the same liquid show increasing contrast (and pH), so you wouldn't have to expend whole rolls on this.

    If my suspicion proves correct, better buffering would help.
    Trying to be the best of whatever I am, even if what I am is no good.

  9. #289
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    Mark;

    We typically used small strips (35mm x 12") to check new coatings and new chemicals out. Then we processed a full roll. I have never seen this happen. These were 1 L to 2 L tanks for the strips and about 2L - 4L for the full rolls. We used both hand agitation (dip and dunk) and Nitrogen burst, and these were all comparable.

    I have no explanation.

    PE

  10. #290

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    Quote Originally Posted by Photo Engineer View Post
    Mark;
    We typically used small strips (35mm x 12") to check new coatings and new chemicals out. Then we processed a full roll. I have never seen this happen. These were 1 L to 2 L tanks for the strips and about 2L - 4L for the full rolls. We used both hand agitation (dip and dunk) and Nitrogen burst, and these were all comparable.
    I have no explanation. PE
    Here are the curves between the test-dev and XTOL. Note that the test-dev *strip* matched XTOL well. On these rolls, I shot the Stouffer wedge twice, the second with longer exposure, and thus was able to catch the shoulders:

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    Notice that XTOL has an abrupt shoulder, and that the test-dev shoulders-off gently, giving more useful dynamic range. We know about the trade-off between contrast/grain/sharpness. I'd like to add another item to that list: dynamic range. This test-dev would show detail in clouds better due to its gentler shouldering.

    Also, I thought I accidentally developed the roll for one minute too long, so I did it again. Here's are the curves for the two rolls:

    Click image for larger version. 

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    This gives you an idea of the repeatability of my work. And it shows that the time is correct (nuts!).

    This dev contains some propylene glycol, which is a difference from XTOL and other dev's that Kodak developed. I noticed that PG retarded development, so my 12.25 minute time increased to 13.1 minutes (keeping pH constant). Ratios of the curves above tell me the time should be 12.1-12.3 minutes, which is where it originally was. Could a roll undo the PG-retarding?

    Mark Overton

    EDIT: Rudi, I'll remember to measure before/after pH for the next roll and see if it rises.



 

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