Ilford Wash Procedue

Discussion in 'Darkroom Developing and Printing' started by Steven Woody, Jun 16, 2007.

  1. Steven Woody

    jch Guest

    _____
    For those of you who enjoy compounding your own solutions, i found this
    substitute formula for Kodak's Hypo Clearing Agent in an old photo book:

    SUBSTITUTE FORMULAS FOR KODAK'S HYPO CLEARING AGENT

    The following formulas are used by the larger labs that mix
    their own solutions:

    WORKING SOLUTION - (not concentrate)
    Water 1.0 liter
    Sodium Sulfite 20.0 grams
    Sodium Bisulfite 0.2 gram

    The Sodium Bisulfite is in the formula only to lower the pH
    to 7 - 7.5 to prevent softening the emulsion of film. If
    papers are to be used, leave out the Bisulfite to deliberately
    get more softening to improve the gloss. Also, to improve the
    paper gloss, leave out all hardening agents in the fixing baths~

    A concentrate of the above would be as follows:

    Hot water 1.0 liter Dilute 1 part conc.
    Sodium Sulfite 200.0 grams with 9 parts water.
    Sodium Bisulfite 2.0 grams

    DIRECTIONS FOR USE

    After normal fixing, transfer prints or films to the clearing
    agent solution with or without a water rinse. The water rinse
    increases the capacity. 200 8x10 (or equivalent) papers or
    150 to 200 8x10 (or equivalent) films per gallon of clearing
    agent solution.

    Water AT 65 to 70 F (18.5 to 21 C)
    Papers Rinse Running
    and After Hypo Clearing Agent Water
    Films Fixer* (With Agitation) Wash

    PAPERS
    SW 1 min. 2 min. 10 min.
    DW 1 min. 3 min. 20 min.

    FILMS 30 sec. 1 to 2 mm. 5 min.

    *Rinse after fixer may be eliminated. Capacity per gallon of
    clearing agent solution will then be reduced to 80 8x10's or
    equivalent for papers and 50 to 60 8x10's or equivalent for
    films.
     
    jch, Jun 18, 2007
    #21
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  2. Interesting. For working solution, the formula
    in Anchell works out to:

    S. Sulfite 20 g / l
    S. Bisulfite 5 g / l

    and claims the Bisulfite should be eliminated when
    glossing prints.

    The formula I use to make concentrate, pinned to
    the corkboard in the darkroom for the past ??? years:

    S. Sulfite 15 g/l 2 tsp/l
    S. Bisulfite 5 g/l 1 tsp/l

    I mix it as a concentrate to dilute to 1:9

    EDTA 1 Tbsp
    S. Sulfite 300 g
    S. Bisulfite 100 g
    Water to 2 l

    The EDTA amount is a WAG (Wild Arsed Guess) based loosely
    on the observation that 1/2 tsp per liter keeps precipitate
    from forming in D-72 stock solution.
     
    Nicholas O. Lindan, Jun 18, 2007
    #22
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  3. My early morning typo, Sodium bisulFITE is the correct
    substance. FWIW, it turns out that when Kodak specifies the
    bisulfite they really mean an impure commercial version of
    this substance which is at least half Sodium Metabisulfite
    which will work in any of the formulas. Actual bisulfite is
    evidently hard to package for some reason.
     
    Richard Knoppow, Jun 19, 2007
    #23
  4. Correction! The correct buffer chemical is Sodium
    BisulFITE, my typing error.

    The patent for KHCA is USP 2,860,978 issued to Richard
    Henn and John I. Crabtree and assigned to Eastman Kodak. The
    formula given in it is:

    Wash Aid Patent Formula (working solution)
    Sodium Sulfite 20.0 grams
    Sodium Bisulfite 5.0 grams
    Sequesterine Na-4 0.5 grams
    Water to 1.0 liter

    Sequestrine is a brand name for EDTA Tetra-sodium salt.
    The MSDS indicates the commercial product also contains
    Sodium Citrate in an amount approximatelly equal to the EDTA
    but MSDS quantities are in ranges of percents rather than
    exact amounts so the amount of citrate might be anywhere
    from 0.1% to 0.5% in solution. The commercial product is a
    powder to make a concentrate. The concentrate is 5 times the
    concentration of the working solution so its formula should
    be:

    Sodium Sulfite 100.0 grams
    Sodium Bisulfite 20.0 grams
    EDTA Na-4 2.5 grams
    Sodium Citrate (probably) 2.5 grams
    Water to make 1.0 liter

    The instructions for KHCA suggest beginning with 750.0 ml of
    water.
    Sodium Metabisulfite will do instead of the Bisulfite.
    According to Kodak and others commercial Bisulfite is mostly
    Metabisulfite and this has been the case practically
    forever.
    It is probable that the sequestering agents can be left
    out, it will depend on the water supply where you are. I
    don't know how serious the problem wtih precipitation of
    sulfite by the aluminum hardener is, perhaps not very. If
    you try the formula without the sequestering agents and get
    a deposit of mineral material on the film or paper then you
    must add them.
     
    Richard Knoppow, Jun 19, 2007
    #24
  5. Steven Woody

    dan.c.quinn Guest

    Sodium thiosulfate anhydrous 16 grams or sodium
    thiosulfate pentahydrate 25 grams in 500ml H2O for one
    roll of 120. That is not a calculated amount. That amount
    was determinded by trial and error. I went through several
    rolls of unexposed film arriving at that amount. Unexposed
    film is worse case for fixer. Be sure and test a roll of your
    film worst case using your procedures.

    Currently I'm testing four DW FB papers; Slavich, Emaks,
    Kentmere, and Arista. At present a 1% solution of sodium
    thiosulfate anhydrous of 320 ml volume looks to do the job.
    The one-shot is very dilute. Perhaps 9 minutes will do;
    depends some what upon the film. I may spend most of a
    day exposing a roll of film. A few minutes more for processing
    means nothing. Besides I don't wish to waste chemistry. Dan
     
    dan.c.quinn, Jun 19, 2007
    #25
  6. The usual fixing bath contains about 240 grams/liter of
    crystaline Sodium Thiosulfate or about 153 grams/liter of
    anhydrous thiosulfate. I am quite skeptical about the
    ability of a dilute fixer solution to provide adequate
    fixing even if used only once.
    I was going to refer you to an old post to this group by
    Michael Gudzinowicz where he explains the fixing process
    quite thoroughly, however, I find Google groups search to be
    a bit of a pain these days to will copy and attach that post
    to this one.

    Mike's post begins here
    -------------------------------------------------------------
    This is part of one of my old replies on fixing, which
    should cover your
    concerns. BTW, use an acid stop bath, since any developer
    carry-over
    (still alkaline) to fixer will results in reduction of
    soluble silver as
    fixing begins, with possible staining and/or fogging as
    likely results.

    (The following are some of my notes on fixing film and
    papers for
    your personal use - not for distribution. Copyright (c)1995
    by
    Michael Gudzinowicz.)


    The basis of fixation and accompanying problems aren't
    treated in
    depth in most texts. This oversight often leads to postponed
    "accidents" whenever people are tempted by a sense of false
    economy to save time or materials. An introduction to the
    underlying chemistry should help to define a more critical
    approach to film and paper preservation, which doesn't rely
    on
    rumor and the advertising literature. The following notes
    were
    taken from Grant Haist's "Modern Photographic Processing,
    Vol.1"
    (Wiley, 1979), "The Theory of the Photographic Process"
    edited by
    T. H. James (3rd & 4th ed., 1st & 2nd edited by C. E. K.
    Mees;
    Macmillan, 1966 (3rd)), "Ilford Monochrome Darkroom
    Practice" by
    Jack Coote, and the research and technical literature.


    Stop Bath:


    Compared to a water rinse, a dilute acidic stop bath will
    stop
    development very rapidly (15 sec) due to the pH change and
    rapid
    tunneling of protons compared, to a water bath where
    developer
    diffusion takes minutes (the basis of water bath
    development).
    The acid stop minimizes developer oxidation in fixers with
    dissolved silver, which prevents soluble silver reduction
    and the
    formation of dichroic fog. Likewise, the pH change retards
    aerial
    oxidation of the developer and oxidation of fixer in the
    emulsion
    by radicals generated from the developer, which degrades
    fixer
    complexes to partially oxidized insoluble products which
    stain
    films and papers, and eventually cause fading and sulfiding.
    Also, acid helps to maintain the pH of the fixer in a region
    where it's stable, and where the hardeners are effective and
    don't precipitate.


    In addition, the use of a stop bath rather than water
    reduces the
    osmotic shock and resultant swelling of the emulsion which
    is
    seen when emulsions with high solute concentrations are
    placed
    into water, and thereby may reduce grain clumping.


    Fixation:


    The common notion is that the fixer removes undeveloped
    silver
    halide by a simple reaction involving the replacement of the
    halide by thiosulfate to form a soluble silver complex, and
    then
    if the film or paper looks or tests "clear", the only
    problem is
    fixer removal. Unfortunately, this is not the case. When a
    film
    is "fixed", a number of complexes are formed between silver
    and
    thiosulfate, and all are in dynamic equilibrium. In
    addition, the
    accumulation of halide during fixation reduces fixer
    capacity
    with use when free silver and halide levels approach their
    limits
    of free, non-complexed solubility.


    A simple table outlining the dissolution of silver in fixer,
    and
    equilibria with fixer is outlined below. The silver halide
    may
    dissociate to a very small degree in aqueous solutions, and
    the
    thiosulfate anion will form a 1:1 complex with the silver
    cation
    (Rxn 1) or the thiosulfate may react directly with the solid
    silver halide crystal (Rxn 1). In either case, the first
    complex
    (I) is >very insoluble< and remains tightly adsorbed to the
    surface of the solid silver halide.


    A second thiosulfate anion may react with the first complex
    (I),
    to form a soluble product (II) with a silver to thiosulfate
    ratio
    of 1:2 (Rxn 2); and then if "free" thiosulfate
    concentrations are
    high, a third thiosulfate anion may react with the soluble
    second
    complex (II), creating a third complex (III) with one atom
    of
    silver and three molecules of thiosulfate which is quite
    soluble
    (Rxn 3).


    Sequence of Complex Formation:


    Note: Charge of ions in () brackets; # of molecules []# in
    the
    complex follows brackets; TS is thiosulfate (hypo) anion;
    Ag,
    silver; Br, bromide. <-> shows equilibrium reactions.


    Rxn 1) Ag (+) + TS (-2) <-> AgTS (-) (first complex (I),
    monoargentomonothiosulate; insoluble - remains adsorbed to
    the
    crystal as it forms)


    Rxn 2) AgTS (-) + TS (-2) <-> Ag[TS]2 (-3) (aq) (second
    complex
    (II), monoargentodithiosulfate; soluble - removed from
    emulsion
    by diffusion)


    Rxn 3) Ag[TS]2 (-3) (aq) + TS (-2) <-> Ag[TS]3 (-5) (aq)
    (third
    complex (III), monoargentotrithiosulfate; very soluble in
    aqueous
    solutions)


    In solution, these reactions are reversible, so all
    complexes are
    present, and a small amount of Ag+ cation is not complexed
    in
    solution. The following equilibria occur:


    Rxn 4) Ag (+) (aq) + TS (-2) <-> AgTS(-) (aq), where all
    components are in solution (aq) and adsorption doesn't
    occur.


    Rxn 5) AgTS (-) (aq) + TS (-2) <-> Ag[TS]2 (-3) (aq) where
    the
    monoargentomonothiosulfate is in solution and not adsorbed.


    Rxn 6) Ag[TS]2 (-3) (aq) + TS (-2) <-> Ag[TS]3 (-5) (aq)
    where
    both the monoargentodithiosulfate and
    monoargentotrithiosulfate
    complexes are in solution.


    As more silver is put into solution with fixer use, more
    complex
    II & III are formed, and the level of the less soluble 1:1
    complex (I) and free silver ion are also increased. After a
    few
    uses of fresh fixer, the less soluble complex (I) and silver
    halide are left in the paper or film at low, but destructive
    levels, although the film appears to clear. Also,
    thiosulfate is
    adsorbed to developed silver grains in papers (iodide tends
    to
    displace it from films). Residual complex I and residual
    thiosulfate adsorbed to silver grains are converted to
    trithionite and higher thionites in a few days, and degrade
    and
    react with silver giving stains (sulfiding) and fog. (Brown
    silver sulfide is seen after bleaching the silver grains,
    and is
    proportional to the developed silver.)


    With progressive use of the fixer, levels of bromide rise,
    as
    well as chloride from papers and iodide from films. Silver
    halides have low solubility, and as the level of bromide or
    iodide rises, it forms silver halide in solution and the
    fixer
    will no longer dissolve silver halide. A number of complexes
    and
    equilibria occur with each halide and mixtures. On a
    relative
    basis, silver chloride is more soluble than bromide and has
    little effect on fixer capacity; silver bromide is less
    soluble
    and determines fixer activity to a significant degree,
    unless
    films with low levels of iodide are fixed, in which case
    fixer
    capacity is reduced significantly due to silver iodide
    insolubility (a problem with T-Max films, treated later). In
    instances where silver is removed to "regenerate" fixers,
    iodide
    accumulation may interfere. Also, in two-bath fixation which
    follows, carry-over occurs, which requires periodic
    replacement
    of both baths.


    The only way to ensure that little AgBr or the insoluble
    first
    complex is left in the paper, is to use fresh fixer with
    little
    accumulated silver and halide, and an excess of
    non-complexed
    thiosulfate to remove it. This approach to archival fixing
    when
    used with one bath is fairly wasteful, though effective.
    Rather
    than using one bath, the same results can be obtained with
    two
    baths, and the capacity of the fixer is far greater.
    Essentially,
    the first bath removes the bulk of the silver and halide,
    and
    leaves traces in the emulsion and paper. This amount when
    carried
    over to a second bath, is insignificant, so the second bath
    always acts as "fresh" fixer with high non-complexed
    thiosulfate
    levels to react with the small amounts of silver halide and
    less
    soluble complexes to speed their complete removal.


    More on Fixing - One and Two Bath Fixation:


    Haist cites the following maximal permissible values for
    one-bath
    film and paper fixers for commercial and archival
    processing:


    One-bath fixation: Commercial Archival


    Film:


    Max. Ag conc.: 1.5g/l 0.2g/l
    Max rolls/gal: 25 rolls/gal 2 rolls/gal
    Non-image Ag in film: 0.01mg/in^2 0


    Paper:


    Max. Ag conc.: 0.3g/l 0.05g/l
    Max. sheets/gal: 30 8x10 5 8x10
    Non-image Ag in paper: 0.005mg/in^2 0


    Essentially, as fixer total silver (free and complexes) and
    halide concentrations rise, the fixer's ability to remove
    all of
    the silver from the paper diminishes markedly, as indicated
    by
    the very limited capacity of one-bath to remove silver to
    archival levels.


    The solution to the limited capacity is to use a fresh
    second
    fixer bath to maintain a very low total silver level, with a
    water rinse between the first and second baths to minimize
    fixer/silver carry-over.


    Two bath fixation: Commercial Archival


    Film:


    Bath 1:
    Max. Ag conc.: 6g/l 3.5g/l
    Max. rolls/gal: 60-70 40


    Bath 2:
    Max. Ag conc.: 0 .5-1.5g/l 0.02g/l
    after 60-70 after 40


    Non-image Ag in film: 0.01mg/in^2 0


    Paper:


    Bath 1:Max. Ag conc.: 2g/l 0.8g/l
    Max. sheets/gal: 200 8x10 70 8x10


    Bath 2:
    Max. Ag conc.: 0.3g/l 0.05g/l
    after 200 after 70


    Non-image Ag in paper: 0.005mg/in^2 0


    The first fixer gets rid of most of the silver, and the
    second
    maintains a very low silver concentration and relatively
    high
    free thiosulfate concentration to remove the remainder of
    the
    insoluble complexes and non-image silver present in the
    emulsion
    after the first fixation.


    The first bath is used for the maximum number of sheets or
    rolls
    indicated, and then discarded after silver recovery. The
    second
    bath is substituted for the first, and a fresh second bath
    is
    prepared. After 5 cycles (substitutions), or one week if
    exposed
    to air in tanks, both baths are replaced. Compare the
    capacity
    for commercial or archival standards using two baths to that
    for
    one... it is far more economical than using one bath, but
    also
    avoids the temptation to over-use fixer, resulting in under-
    fixation and difficult removal of insoluble complexes.


    Films:


    With films, the fixation time in the first fixer should be
    at
    least twice the clearing time... likewise for the second
    bath.
    The clearing time should be checked often if that approach
    is
    used, however, Kodak recommends 5-10 minute fixation with
    non-
    rapid fixers and most films. Since there is no danger in
    longer
    fixing times, incorporating a five minute fix in each bath
    into a
    "normal" development procedure may avoid problems and
    provide
    some security. Agitation should be constant to remove fixer
    from
    the surface of the film to facilitate diffusion, however,
    increased agitation never can replace adequate fixing time
    or
    counteract the cumulative effects of re-using fixer. With
    rapid
    fixers, there is little "danger" of bleaching film with 5-10
    minute fixation... also, if standard procedures are used,
    any
    minimal bleaching would never be noticed, since it would be
    incorporated into tests for contrast and development time.
    With
    T-Max films, Kodak recommends longer times. For instance,
    they
    suggest that it is "safe" to check clearing at five minutes
    with
    standard fixers or three minutes with rapid fixers... and
    total
    fixing time should be twice the clearing time. (Kodak's
    "advice"
    on T-Max varies from simplistic on 35 mm film boxes, to
    warnings
    in detailed technical literature, not only on times, but
    also on
    fixer replenishment rates for processors.)


    T-Max Films:


    With some films, such as Kodak's T-Max series, fixer
    capacity is
    reduced to one-half of what one normally expect, and fixing
    times
    are extended to twice the usual time, since silver iodide is
    resistant to fixation. In Kodak publication F-32 on T-Max
    films,
    Kodak indicates that a magenta stain may be left in the
    emulsion
    with inadequate fixing, and recommends further fixing with
    fresh
    fixer to remedy the problem. (The magenta sensitizing dye is
    adsorbed to the silver halide (EKC statement - not
    speculation);
    when the halide is fully dissolved, the dye is removed.) In
    some
    instances, the dye can be removed by treatment with
    hypo-clear,
    which may contain sulfite or high salt concentrations which
    can
    act as weak fixers in addition to displacing hypo, or with
    prolonged water washes. The "stain" problem isn't whether it
    will
    interfere with variable contrast paper filtration or not,
    but its
    indication that the film isn't fixed properly.


    Papers:


    For paper fixation, do not use fixer which has been used for
    film. It is difficult to track capacity accurately (see
    table
    above... silver capacity differs for film and paper), fixer
    dilution may vary between paper and film fixers, and the
    "sudden"
    accumulation of iodide after developing films may greatly
    prolong
    paper fixation or may leave insoluble silver iodide behind
    unless
    one tests clearing times at every session.


    The clearing time for papers may be determined
    experimentally or
    by manufacturer recommendation (for Ilford, see below).
    Fixing
    times for most fiber papers is on the order of five minutes
    for
    each bath, with an intervening water rinse and storage in
    water.
    To save time, prints can be fixed in the first bath, rinsed
    and
    held in water, then fixed in the second bath at the end of a
    session. As mentioned, long contact with fixer can cause
    problems
    if fixer enters the paper fibers (not between them). Papers
    and
    fixers vary, and it is best to use at least the minimum time
    recommended by the paper manufacturer. Kodak recommends 10
    min
    for fiber base and 2 min for RC in one bath, or half that
    time
    for each of two baths. The RC time is optimistic, though
    five
    minutes per bath is reasonable for fiber papers. Prolonged
    contact with rapid fixers will slowly bleach an image or
    cause
    uneven bleaching if prints remain in rapid fix without
    agitation
    for prolonged times (1/2 hr+).


    In any case, paper and film should be promptly removed from
    the
    second fixer, rinsed, and placed in a water bath until
    treated
    with a hypo clearing solution to displace free thiosulfate.


    Rapid Fixer:


    Rapid fix has the advantage of a shorter contact time, and
    that
    may minimize the penetration or degradation of fixer in the
    paper's fibers. Also, the useful capacity of rapid fixers is
    fairly high... 10-15 g/l silver vs. 6g/l for films or 2 g/l
    for
    papers using regular fixers (James; Haist table above for
    bath 1
    of a two bath sequence). However, there is little data to
    extrapolate those numbers into increased capacity _without
    risk_
    of problems. In that regard, Kodak's recommendation for
    capacity
    of rapid fix and other fixers is nearly the same (100-120
    sheets
    or rolls), which is optimistic for one bath commercial
    processing.


    Hardeners:


    For film, a hardening fixer is often preferred to minimize
    any
    emulsion damage in handling. The only advantage of rapid fix
    with
    film is decreased processing time and perhaps, decreased
    rinse
    time. Non-hardening fixers are also preferred for
    development of
    the stain with pyro developers.


    For paper, rapid fix without hardener is often preferred,
    and
    gives better results with toning. Paper curl seems to be
    minimized and there is less danger of "breaking" the
    emulsion
    when prints are flattened or mounted. Also, the avoidance of
    alum
    may reduce silver complexes bound in the emulsion. (To
    remove
    hardener for toning: household ammonia diluted 1:10 (0.3%)
    for 2
    min with 45 min wash; or 5 min in 2% solution of Kodalk or
    sodium
    carbonate, then wash).
     
    Richard Knoppow, Jun 19, 2007
    #26
  7. No point fite'ing over it, misspellings are fate'ed
    to happen.
     
    Nicholas O. Lindan, Jun 19, 2007
    #27
  8. Steven Woody

    Steven Woody Guest

    what size of paper and how many sheets of these papers will a 320ml 1%
    hypo solution do?
     
    Steven Woody, Jun 19, 2007
    #28
  9. Steven Woody

    dan.c.quinn Guest

    That 3.2 grams of sodium thiosulfate anhydrous
    will fix one 8x10. I'm ready to start a new series of
    tests on the four papers I mentioned. I messed up on
    a first series of test by introducing more than one
    variable through the series of tests.

    I've had more than one indication that carbonating the
    fix noticeably speeds fixation and washing. I'll post back
    in a few days with some results and additional confirmation
    of what already has been claimed. Dan
     
    dan.c.quinn, Jun 19, 2007
    #29
  10. Steven Woody

    Lloyd Erlick Guest

    June 20, 2007, from Lloyd Erlick,

    I've been operating my darkroom without acid
    for years now, and I find Richard's comments
    (below) absolutely accurate. In fact, his
    first paragraph is essential.

    I have to add something important, though --
    the incredible ease and simplicity of it all.
    Plain fixer is easy and quick to make up,
    rinsing in tap water is a lot easier than
    preparing acid stop, never mind smelling it.

    Shorter wash time requirements from non-acid
    fix, coupled with sulfite washaid, can very
    easily result in rigourously correct,
    'archival' prints. It's just easier and less
    effort without acid.

    My hatred of sulfur dioxide and hydrogen
    sulfide made my decision!

    regards,
    --le
    ________________________________
    Lloyd Erlick Portraits, Toronto.
    website: www.heylloyd.com
    telephone: 416-686-0326
    email:
    ________________________________
    --


    On Sun, 17 Jun 2007 00:59:16 GMT, "Richard

    ....
     
    Lloyd Erlick, Jun 20, 2007
    #30
  11. The evolved gas is important. If you are sensitive to
    Sulfur dioxide that can be enough to justify using an all
    neutral process. The problem is that acid fixing baths
    constantly emmit a small amount of Sulfur dioxide. Some
    people are very sensitive to this gas which can set off
    Asthmatic attacks and cause a choking sensation even in
    those without asthma. Hydrogen sulfide is the gas with the
    rotten-egg odor. It can result from fixing baths which are
    nearing exhaustion but is not usual. It is more often
    encountered when using certain kinds of sulfiding toners.
    Any solution which emmits Hydrogen sulfide should be used in
    a very well ventillated place, even outdoors and should be
    kept away from unprocessed sensitive materials because the
    gas is a prolific fogging agent.
    A non-hardening fixing bath can still be acid but can be
    less so than a hardening bath. The acid condition of the
    hardening bath must be right for the hardener to work.
    Without the hardener the fixer can be just acid enough to
    inactivate carried over developer. Low acid fixer is much
    less likely to produce irritating gasses.
     
    Richard Knoppow, Jun 21, 2007
    #31
  12. Steven Woody

    Lloyd Erlick Guest



    June 24, 2007, from Lloyd Erlick,

    Maybe PW mixed at twice the recommended
    concentration??

    I've always just used a two percent solution
    of sodium sulfite.

    regards,
    --le
    ________________________________
    Lloyd Erlick Portraits, Toronto.
    website: www.heylloyd.com
    telephone: 416-686-0326
    email:
    ________________________________
    --
     
    Lloyd Erlick, Jun 24, 2007
    #32
  13. Steven Woody

    dan.c.quinn Guest

    And I've been plugging Agfa's recommended
    sodium carbonate. What happened? Dan
     
    dan.c.quinn, Jun 25, 2007
    #33
  14. This is a pretty old thread now but I will add a bit
    anyway. The Agfa recommendation is based on work done in its
    labs in the 1930's. Its well known that treating film in a
    mild alkaline bath will increase washing rate especially
    when its been fixed in an acid fixing bath. As I stated in a
    previous reply the pH change affects the electric charges in
    the gelatin so that they do not attract the Thiosulfate ions
    but rather repel them. It also breaks the bond caused by
    Aluminum sulfate hardener, however, it also destroys the
    hardening effect. A plain alkaline bath, however, does not
    have the ion-exchange properties of Sodium Sulfite. It is
    this ion exchange effect which causes Sulfite to have such a
    strong accelerating effect on washing. Of course, sulfite is
    also mildly alkaline. The buffering to neutral pH in Kodak
    Hypo Clearing Agent is about optimum for washing because it
    eliminates the bonding caused by aluminum hardener without
    destroying the hardening action.
    While Agfa recommends 2% Carbonate nearly any mild
    alkali, such as 2% Borax, will do if one wants only the pH
    adjustment. However none will be as effective as the Sulfite
    bath.
     
    Richard Knoppow, Jul 3, 2007
    #34
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