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  1. #1

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    Why two alkalis in a solvent developer?

    Crawley's FX-15 for example includes both Borax and Sodium Carbonate. The formula also includes Sodium bisulfite so I assume this is acting with either the Borax or Carbonate as a buffer. But which? What is the target pH of FX-15?

    Thanks
    Michael

  2. #2
    Ian Grant's Avatar
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    Crawley's own developers and in fact entire chemistry is somewhat enigmatic. I had a couple of business lunches with two chemists who made pilot batches for some of the Paterson chemistry he formulated and what they told me was a real eye-opener

    The way I was told it was his chemistry worked as he wanted it to but there were far better, simpler and consequently cheaper ways to get the same results.

    I used Acutol-S in the 70's it was an awful developer for 35mm because it was grainy with big edge effects, but with 120 possibly OK, no-one using LF back then would have used Paterson chemisrty as it was aimed at the amateur market. In the 60's & 70's there was no amateur tradition of usinf LF cameras. WWII had brought a sea change in approach in the UK and probably the rest of Europe. 35mm & 120 were the King, LF was just a professioanl set of formats.

    Ian

  3. #3

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    Thanks for the insight, Ian. I would say I've always enjoyed reading about Crawley's developers, his "rules of thumb" etc, but I've never actually used one. Every now and then I seem to get the urge to experiment with some specific formulas of his, but in the end I never get around to it.

    One thing's for sure, in Anchell/Troop Crawley's formulas are held in high regard. It appears he paid careful attention to formulate developers for specific types of film, tabular emulsions etc. So on the surface at least, it would seem his general line of reasoning supports the notion developers need(ed) to change as films changed (I'm recalling PE's myth #15 as I write this).

    Michael

  4. #4
    Ian Grant's Avatar
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    Crawleys long article "Notes on Present Day Monochrome Emulsions and their Development" which was puplished in 8 sections in the BJP (then a weekly publication) between Dec 2nd 1960 and Jan 27th 1961 and is a significant over-view of film development of that era. There's no doubt that a very significant amount of work went into the research and subsequent testing of the formulae.

    Back in the 70's and 80's many questioned why some of his published developers (six out of about 18) contained three developing agents, Metol, Phenidone and Hydroquinone when in practice using either Metol or PPhenidone with the Hydroquinone would have been simpler. He did in fact remove the Metol from FX6 (a Monobath) the new formula FX-6a worked just as well.

    Quote Originally Posted by Michael R 1974 View Post
    It appears he paid careful attention to formulate developers for specific types of film, tabular emulsions etc. So on the surface at least, it would seem his general line of reasoning supports the notion developers need(ed) to change as films changed
    The developers for tabular emulsions came very much later and in a way just mirror other manufacturers like Kodak and Ilford who had also introduced new developers like Tmax dev, Xtol, DDX etc which give better film speed or finer grain etc with these newer films than D76/ID-11.


    It's important to remember that few of Paterson's developer formulae have been published, FX15 Acutol S is one of the exceptions, the first of Crawley's developers to be sold by Paterson - Acutol - went on the market nearly three years after the publication of his artice. By then Crawley was editor of the British Journal of Photography a position which gave him strong links to most major manufacturers in the photographic field.

    In the early years Paterson's B&W chemistry was manufactured for them by Ilford, at the same time (1963) they had close links with another important phot-chemist Dr Curt (Kurt) Jacobson and where selling his companies Pavelle colour materials - paper and chemistry as Paterson Pavell.

    Curt Jacobson wrote what's still about the best book on all aspects of film processing "Developing" which went into 18 editions each with many reprints over a period of about 36 years. He makes little mention of the FX series of developers.

    Ian

  5. #5

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    Very interesting - thanks for the feedback.

  6. #6

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    Many years ago it was fairly common place to use a combination of carbonate and bisulfite in developers. The resulting bicarbonate ion acts like a restrainer/antifoggant although not as powerful as bromide.
    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

  7. #7

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    It is interesting so many of Crawley's developers include a bromide restrainer, particularly in formulas with borates where he claimed it was necessary to prevent the reduced definition he associated with borate alkalis. This would still seem to contradict Haist's view regarding the use of restrainers in general. Although I suppose I'm oversimplifying this somewhat.

  8. #8

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    I believe it is better for stable pH that the buffer concentration be large.
    So bisulfite-borax-carbonate, as in FX 15, will be a better buffer than bisulfite-carbonate alone.



 

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