Much or little Metol?

Discussion in 'Black and White' started by j._patric_dahl_n, May 31, 2001.

  1. I've seen many recipes for developers. Some contains 2-4 grams of Metol and others use 7-10 grams. Same with Glycin. I like Agfa 8 that contains 2 grams Glycin, but some recipes use 10 grams or more. What's the point of using more of the developing agents? Is it that the developer can be used longer, or does it affect the results?
     
  2. The composition of the developer typically is based on the intentions
    of the designer i.e., what kind of trade-off one is trying to make.
    Compare, for example, two metol based developers - D23 and FX1. The
    developers are designed for quite different effects and the tradeoffs
    required are different. D23 is designed as a fine grain developer and
    uses sulfite as a silver solvent - the solvency is key to achieving
    the fine grain. For sulphite to act as a silver solvent, it needs to
    be present in fairly large amounts (I believe you need at least
    50gms/litre to start noting solvency effects). D23 contins 100 gms of
    sulphite. Solvency is also affected by the length of time the film
    stays in contact with the solvent. Therefore, to balance the formula
    i.e., have the film in for some optimum window of time, one needs to
    adjust either the amount of developing agent or the alkali. D23 uses
    sulfite itself as the alkali (and the virtue of D23 is its simlicity
    and preservation - in fact, Henn formulated D23 as a simpler, more
    reliable alternative to D76). In other words, other characteristics
    desired in the developer dictate the decision of no other alkali.
    This leads to the requirement of a fairly high amount (7.5 gms) of
    the developing agent, metol.

    <p>

    In comparison, FX1 is also a metol based developer but was explicitly
    formulated to provide the maximum adjacency effects possible. The
    mechanism that is utilized for this is the controlled exhaustion of
    the developing agent. This is achieved by having a small amount of
    the developing agent, a small amount of sulfite and using an alkali
    to accelerate the rate of development. It is worth pointing out here
    that different formulae use different methods to achieve adjacency
    effects. For example, HDD uses larger amounts of the developing agent
    (2gms/L) while reducing sulphite (1gm/L) to provide controlled
    exhaustion by reducing sulphites protective action, while FX1 uses
    lower amount of developing agent and a slightly higher amount of
    sulphite to provide the controlled decomposition.

    <p>

    In sum, it is the interactions of various components of the developer
    that provide the characteristics of that developer. So, things are
    more complicated than it appears at first sight - there does not seem
    to be an easy way to arrive at optimum levels for all criteria.
    However, the flip side of the coin is the increased flexibility one
    has in formulating developers.

    <p>

    Cheers, DJ.
     
  3. Very nice description DJ!

    <p>

    Regards,
     
  4. Thanks for the great explanation!
     

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