To Richard K - Perceptol x Microdol

Discussion in 'Darkroom Developing and Printing' started by Jorge Omar, May 31, 2004.

  1. Jorge Omar

    Jorge Omar Guest

    Hello, Richard

    Could you comment in the (accepted) data that Perceptol uses an innordinate
    ammount of bromide vs Microdol using chloride?


    Jorge Omar, May 31, 2004
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  2. This is true according to the Material Safty Data Sheet
    on the Ilford web site. Microdol-X contains sodium chloride.
    Both the chloride and bromide act as fine grain agents in
    large amounts. I _think_ I saw an old MSDS for Perceptol
    which showed sodium chloride instead of bromide but am not
    sure and can't find it in my archived stuff. Haist mentions
    sodium chloride in his book but not bromide as a fine grain
    Both developers have proprietary formulas but the
    chloride content of Microdol-X is evidently about 20 grams
    per liter. There was an earlier version called just
    Microdol. I don't know the difference for certain but think
    that the X version probably contains something to prevent
    dichroic fog. It may be that the bromide in Perceptol also
    does this.
    Both of these developers work as advertised. 100 T-Max in
    full stength Microdol-X is nearly as fine grain as Technical
    Pan in Technidol at more than double the speed and is less
    fussy about getting normal tonal range.
    Richard Knoppow, Jun 1, 2004
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  3. I'm a long way from last using either dev, but from my early experiences
    I would have expected bromide or chloride to have acted as mild solvent
    agents with a restraining and buffering side-effect, with slightly more
    activity from bromide.

    Perceptol, which I used for a long time both straight and diluted,
    generally had a far superior resistance to aerial oxidation, and with
    the long dev times involved for 1+3 user (an extreme) with inversion
    agitation, that was technically better. Microdol-X generally proved
    slightly harder to dissolve, with more tendency to leaving a small
    residue needing filtering, and oxidised more rapidly in stock solution
    or diluted working solution.

    Kodak used the 'X' suffix to indicate films or processes which were in
    line with sensitivity revisions - originally, the X was used to indicate
    filmspeeds only. X indicated a speed approximately 32 ISO (pre-war), XX
    64, XXX 125. With the changes in calculaton of filmspeeds using density
    above fog threshold in the 1950s, X became 64, XX 125 and XXX 250;
    further improvements in emulsions meant that Tri-X (XXX) increased to
    320 - the rating which still applied to Tri-X Professional into the
    1980s - and then 400 for general stock. Panatomic-X remained peculiarly
    stuck in the past and was only 32 ASA (ISO) and eventually the whole
    concept just got muddled so that no-one really remembers why Tri-X is
    called Tri-X! Plus-X, or course, was a little bit faster than X in the
    final stages where X meant 100, XX 200 and XXX 400.

    Whatever formulation changes were present, the X in Microdol-X probably
    got there as part of a marketing concept, and indicated the suitability
    of the developer for use with these films - but also implied a retention
    of filmspeed. Though Microdol-X (like Perceptol) incurs a loss of around
    1/3 to 1/2 the conventionally measured filmspeed unless diluted, it was
    in its day far superior to strong solvent developers, which lost half to
    2/3rds of available speed and also produced a very low acutance by
    destroying micro-contrast. But strong solvent developers were not averse
    to using sodium thiosulphate in the dev, being half way to a monobath.

    So the X probably just marked the spot... signalled that this was a
    fitting companion dev to Panatomic-X, Plus-X and the 'generation X' of
    films with their revised sensitivities.

    For anyone keen on experiment, in the 1970s I made an ad-hoc special
    effect developer by mixing a chromium intensifier bleach with a print
    strength MQ developer - in much the same way as a monobath. Negatives
    developed in this produce a direct posterization, with a distinct set of
    steps, but you have to start the development in a regular developer then
    transfer to the combined intensifier/redeveloper mix for the second half
    of the dev time.

    David Kilpatrick, Jun 1, 2004
  4. Jorge Omar

    Jorge Omar Guest

    Thanks for the explanation, but I still find it intriguing how a
    developer works with such a hig ammount of restrainer in it!

    Jorge Omar, Jun 2, 2004
  5. I doubt that. Sodium sulphite rather than potassium bromide. The
    latter is seldom used at concentrations exceeding 3g/litre in B&W
    Michael Scarpitti, Jun 2, 2004
  6. message
    Have a look at the MSDS. Perceptol contains a very large
    amount of bromide. I think the bromide in Perceptol and
    chloride in Microdol-X have about the same effect. They slow
    down the development. Neither is a halide solvent. There is
    considerable solvent action in both developers due to the
    high concentration of sulfite and long time of development.
    However, the effect of sulfite as a solvent is very often
    mis-understood. Sulfite has no significant action on the
    developed silver. Nor does it etch the corners off silver
    crystals. Rather, it removes a layer from the surface of the
    halide crystals and changes the shape of the developed
    metallic silver crystals. A small amount of solvent action,
    about what is found in D-76, causes an increase in film
    speed by exposing more development centers to the developer.
    More action, as in Microdol-X, Perceptol, or D-25 when they
    are used at full strength can dissolve some of the
    development centers, or in other words, destroy some of the
    latent image, causing a loss of some speed. When diluted
    this effect does not take place. Note that the developing
    times for these developers is quite long in comparison to
    developers without an extra-fine-grain property. This is the
    result of the very low activity of all three. The same thing
    is found in the old Para Phenylenediamine developers. PPD is
    very low in activity, about the lowest of any practical
    developing agent, and it is a halide solvent. A pure PPD
    developer may take more than half an hour to develope even
    modern film and will lose four or five stops. It does have
    finer grain than any other developer but the great speed
    loss and generally very low contrast made it impractical.
    Most of the practical PPD developers combined it with
    something else, often Glycin or Metol. These developers had
    no advantage over developers like D-25, Microdol-X, or
    Perceptol so fell out of use.
    Grant Haise discusses extra-fine-grain developers a
    little in his book _Modern Photographic Processing_. This
    book, which was long out of print, is available in an
    excellent reprint from the author.
    Richard Knoppow, Jun 3, 2004

  7. Do you have an URL or any information about this? I searched
    in Google, but found only numerous references to the old

    Martin Jangowski, Jun 3, 2004
  8. Martin, I will post the info when I get home and can look it up. I
    got my copy from Grant.

    Richard Knoppow
    Los Angeles, CA, USA
    Richard Knoppow, Jun 16, 2004
  9. Available from (great site for used & obscure books).
    $490 the set, though.
    Nicholas O. Lindan, Jun 16, 2004
  10. The MSDS that I have for Perceptol is: Metol, Sodium Sulphite, Sodiu
    Chloride and Sodium Tripolyphosphate. This developer may correspon
    with the Edgar Hyman Microdol substitute formula published in the Fil
    Developing Cookbook by Steven G Anchell and Bill Troop.
    The MSDS for Microdol-X reads as Elon/Metol, Sodium Sulphite, Bori
    Anhydride, Sodium Chloride and Sodium Hexametaphosphate(Calgon).
    You can find the components used for many Kodak developers on and likewise with Ilford chemicals on
    Keith Tapscott., Mar 17, 2005
  11. "Keith Tapscott."
    Well, well, very interesting. I was sure I had an older
    MSDS for Perceptol showing the above but the later MSDS
    showed Potassium or sodium bromide rather than chloride.
    That puzzled me. Chloride is a known fine grain agent. I
    wondered if there was perhaps an error. I will check the
    Ilford site later. If its sodium chloride then Perceptol and
    Microdol-X are virtually identical, which is what I used to
    The Edgar Hyman formula was published and is mentioned by
    Grant Haist in _Modern Photographic Processing_. I think
    there may also be a patent for the formula or something near
    Sodium tripolyphosphate is a sequestering agent for
    mineral salts in the water as is Calgon. Calgon is also a
    good alkali for developers. Boric anhydride becomes Boric
    acid in solution probably used to adjust the pH and act as a
    Constituents present in very small amounts may not have
    to be shown on an MSDS, especially if they are not
    considered hazardous. Microdol-X is supposed to have a
    silver sequestering agent, perhaps a mercaptan, to prevent
    dichroic fog and excessive physical development from the
    dissolved silver halide. This is the difference between the
    original and the X version. My guess is that Perceptol has
    something similar in it for the same reason.
    Either of these developers, when used full strength, on a
    film like 100T-Max, Delta 100, or Fuji Acros, will produce
    negatives rivaling Kodak Technical Pan for fine grain but
    with considerable more speed (around ISO-50) and no trouble
    from excessive contrast.
    Richard Knoppow, Mar 22, 2005
  12. Calgon etc. are sequestering/chelating agents and
    should prevent dichoric fog.

    I am pretty sure mercaptans aren't used in M-X, or any
    other B&W photographic chemical. We would all
    notice if they were:

    Where they are variously described as smelling of
    rotting animal matter, flatus, skunk and cut onions.
    Nicholas O. Lindan, Mar 22, 2005
  13. Mercaptans are sulfur related compounds. Some are indeed
    foul smelling, in fact, the common odor of cooking gas is a
    mercaptan delibrately added to aid in discovering leaks
    because the gas itself has no odor. However, mercaptans and
    other sulfur compounds are also very important in
    photography. Mercaptans are used as an anti-fog agent
    because they preferentially bind silver halide. Grant Haist
    discusses this in some detail in _Modern Photographic
    Processing_. Calgon and Tripolyphosphate bind carbonates
    like the calcium and magnesium carbonate found in hard water
    but probably are not very effective in binding silver
    halide. Haist suggests that the added ingredient in the X
    version of Microdol is a mercaptan but it is speculation, it
    may very well be something else. Anti-foggants like bromide
    and Benzotraizole are not effective on the soluble silver
    which causes dichroic fog.
    Richard Knoppow, Mar 22, 2005
  14. "Keith Tapscott."
    On checking my files I find I have the current MSDS and
    it does list Sodium Chloride. I strongly suspect the MSDS
    Ilford has had on the web for the last several years,
    listing a large amount of sodium bromide, was in error. The
    current MSDS indicates Perceptol and Microdol-X are either
    identical or close enough to make no difference.
    BTW, the MSDS for "part 1", which has the Metol in it,
    describes it as "brown powder". Evidently, Ilford expects
    some oxidation of the Metol. Metol, when fresh is white or
    very light gray. It can oxidize very quickly in the absense
    of a protective agent. For instance, the normal color of
    Dektol when fresh mixed is light straw yellow. Using water
    that has been boiled and allowed to sit and cool will
    minimise this because the boiling removes much of the
    dissolved gasses. Metol will not dissolve in a concentrated
    solution of sulfite, which is why it is dissolved first in
    developer formulas, but adding about 5 grams of sulfite per
    liter of water will not interfere with its solution and will
    absorb some of the free oxygen in the water.
    Richard Knoppow, Mar 22, 2005
  15. Jorge Omar

    Jordan W. Guest

    Mercaptans (thiols) are not always foul-smelling -- if the vapour
    pressure is low enough the odour may be indetectable. The amino
    acid cysteine, one of the basic amino acids that makes up all
    proteins, is a mercaptan and its decomposition is source of the
    'rotten egg' odour in rotting eggs. But cysteine itself is
    odourless because it is usually found as a salt. It could be that
    Perceptol/Microdol contain a very trace quantity of a mercaptan in
    a non-volatile form.

    Anions of divalent sulfur (mercaptans and inorganic sulfides) have
    a high affinity for silver and form stable complexes with it. This
    is why silver tarnishes in air so readily (silver tarnish is silver
    sulfide from adventitious H2S in the air) and why sepia toning is
    so good at protecting B&W prints and film.

    A story: I heard that, many years ago, a researcher in the McGill
    University chemistry department was doing an experiment involving
    t-butyl mercaptan (the stuff added to natural gas to enable leak
    detection). He failed to adequately condense/trap the reaction
    mixture and as a result vented some of the mercaptan into the
    fume-hood exhaust. Apparently, that day, the Montreal Fire
    Department got dozens of calls from all over downtown Montreal
    reporting gas leaks! That's how pungent the stuff is.
    Jordan W., Mar 23, 2005
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