Barry Thornton 2 Bath questions

Discussion in 'B&W: Film, Paper, Chemistry' started by ParkerSmithPhoto, Nov 6, 2012.

  1. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    Has anyone converted the Barry Thornton two bath higher definition formula to tablespoons or teaspoons? I don't have a gram scale and would prefer not to buy one if it's doable with standard measurements. Most of the scales on Amazon are only accurate to one gram, meaning that the 6.25 grams of metol may just be a ballpark anyway. If in your opinion these amounts are hypercritical and cannot be estimated through teaspoons, etc., please let me know.

    Also, I assume that for Bath A, you mix the metol in first, and then add the sodium sulphite. Is that correct?
     
  2. Gerald C Koch

    Gerald C Koch Member

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    The problem with teaspoon measurement is that it depends on the density of the chemical and also its form. A powdered chemical will have a different density than the same chamical in the form of large crystals. Perhaps you could get a friend to measure the weight of known volumes of your chemicals. Then you would be OK until you bought more.
     
  3. Alan W

    Alan W Subscriber

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    "The metric system is the tool of the devil.My car gets 40 rods to the hogshead"Abe Simpson.
     
  4. Stephanie Brim

    Stephanie Brim Member

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    Gram scales of the sensitivity you'd need (probably to the .01g level) are decently cheap. I highly suggest just getting one.
     
  5. David Allen

    David Allen Member

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    Hi there,

    I bought an electronic jeweler's scale (accurate to 0.1g) for 8€ on e-bay and it was well worth it. Previously I had used mechanical scales and they were a pain. Trying to 'guestimate' with a teaspoon is simply not worth it. Afterall, with Bath B, getting the measurement wrong would affect the final contrast. (With BTTB, the Sodium Metaborate in Bath B can be varied to adjust contrast).

    As to mixing Bath A, you add a pinch of the Sodium Sulphite to the water before adding the Metol and, when fully dissolved, then the rest of the Sodium Sulphite. It helps to have the water pretty hot.

    The simplicity of making BTTB developer and the consistency of the results require that you weigh the chemicals accurately. Therefore, you need to buy a good set of scales. It is a very good investment because mixing your own chemicals will save you so much money and you can 'tweak' your formulae to suit your own needs.

    Best,

    David
    www.dsallen.de
     
  6. doughowk

    doughowk Subscriber

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    As to Metol in water, I believe I've seen recommendations of adding a pinch of the sulfite first before adding the Metol.

    As to scales, I picked up quite cheaply a balance-type scale from chemistry classroom. Should be easily found in usual sites.
     
  7. presspass

    presspass Member

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    Also, in Edge of Darkness, he changed the formula slightly to 6.5 g of metol in Bath A. The developer works well and with little fuss but I use longer times than he recommended - about 5.5 to 6 minutes for Bath A and four minutes for Bath B.
     
  8. Jim Noel

    Jim Noel Member

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    You are correct. Eliminate the pinch of sulfite prior to metol and the metol may never go into solution.
     
  9. michael_r

    michael_r Subscriber

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    That's not the reason. The pinch of sulfite is to help slow down the oxidation of the Metol while it is being dissolved in water. You use a "pinch" because Metol will not dissolve in a solution with a lot of sulfite. So the remainder of the sulfite is added after the Metol is dissolved.
     
  10. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    That's precisely what I needed. $10 on Amazon. Thanks!
     
  11. Patrick Robert James

    Patrick Robert James Subscriber

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    This is a good one. Make sure you get a calibration weight too....

    http://www.myweigh.com/440z.html

    Measuring in tea/tablespoons is only good for non important chems like fixers or stop baths.
     
  12. nworth

    nworth Subscriber

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    That sounds like lousy fuel economy. How many furlongs per fortnight are you running at?
     
  13. pentaxuser

    pentaxuser Subscriber

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    Only 40 rods!! That's very wasteful I blame the cheap fuel policy in the U.S. Actually chains, rods, poles( they are interchangeable)and then furlongs and acres all have a logical interconnected basis going back to the Middle Ages. Trouble is we no longer need to rely on medieval measurements which belong to times when precision and easy division wasn't required. Most couldn't read or write never mind do any math,. Add the "s" if you are in the U.K.

    If I were in the business of mixing my own stuff I'd get a machine that weighed in divisions of 0.1 grammes.

    You wouldn't guess temps so why guess weights as little as a tenth of a gramme which in some cases are more critical

    pentaxuser