Why two step fixing is a Really Good Thing

Discussion in 'Black and White' started by discpad, Mar 8, 2004.

  1. Subject: Why two step fixing is a Good Thing

    While looking at the thread entitled Again a purple tri-x question

    I was led to an interesting article about two stage fixing ...And I Highly Recommend reading it.


    "taco*boy" <ses_2@snet.net> wrote: >Is fixer
    OK to use over and over and over? I've heard that> fixer will turn
    fixer purple when depleted. I have never seen this. >Am I
    wasting fixer I throw it away and it's still clear?

    The best option is to use two fixer bath fixation. The rationale
    is outlined below, taken from one of my old posts.


    Post Development Processing

    ©Copyright 1998 by Dr. Michael J. 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.

    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 is in () brackets; the # of kinds molecules
    [kind of molecule]# in the complex follows brackets; TS is
    thiosulfate (hypo) anion; Ag is silver; Br is bromide. <->
    shows equilibrium reactions.

    Rxn 1) Ag (+) + TS (-2) <-> AgTS (-)

    AgTS (-) is the first complex (I) called monoargentomonothiosulate
    since it contains one silver cation and one hypo anion; it is
    insoluble and remains adsorbed to the crystal as it forms.

    Rxn 2) AgTS (-) + TS (-2) <-> Ag[TS]2 (-3) (aq)

    Ag[TS]2 (-3) (aq) is the second complex (II) complex formed by the
    addition of another thiosulfate anion to monoargentomonothiosulate to
    form monoargentodithiosulfate. The second complex is soluble in
    aqueous solutions and is removed from the emulsion by diffusion.

    Rxn 3) Ag[TS]2 (-3) (aq) + TS (-2) <-> Ag[TS]3 (-5) (aq)

    Ag[TS]3 (-5) (aq) is the third complex (III) called
    monoargentotrithiosulfate since it has three thiosulfate anions
    complexed with one silver cation. It 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 also 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.
    However, in solution the concentration of monoargentomonothiosulfate
    in this and the preceeding aqueous reactions are very low since it's
    nearly insoluble.

    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
    complexes 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 developed silver grains are
    converted to trithionite and higher thionites in a few days, and then
    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 very
    low solubility, and as the level of bromide or iodide rises, it forms
    silver halide crystals 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 containing 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 ocurs,
    which requires periodic replacement of both baths.

    The only way to ensure that little silver bromide (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 free thiosulfate to remove it. This approach to
    archival fixing when used with one fixer bath is fairly wasteful,
    though effective.

    Rather than using one fixer 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 of silver halides and the first insoluble
    complex in the emulsion and paper. The amount when carried over to a
    second fixer bath is insignificant in comparison to the amount of
    free thiosulfate, 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 from the emulsion.


    More on Fixing - One and Two fixer Bath Fixation:

    Grant Haist, the former director of research at Kodak, cites the
    following maximal permissible values for one-fixerbath film and
    paper fixers for commercial and archival processing:

    One-fixer bath fixation: Commercial Archival

    Film:

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

    Paper:

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

    Essentially, as fixer total silver (free and complexed) 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-fixer 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. Some older texts even suggest a fresh third
    fixer bath .


    Two bath fixation: Commercial Archival

    Film:

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

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

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


    Paper:

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

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

    Non-image Ag in paper: 0.005 mg/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 fixer bath is used for the maximum number of sheets or
    rolls indicated, and then discarded after silver recovery.

    The second fixer bath is substituted for the first, and a fresh
    second bath is prepared.

    After 5 cycles (substitutions), or one week if continuously exposed
    to air in tanks, both baths are replaced. Compare the capacity for
    commercial or archival standards using fixer two baths to that for
    one. Two bath fixation is far more economical than using
    one fixer bath , and avoids the temptation to over-use fixer which
    results in under-fixation and difficult removal of insoluble
    complexes which destroy prints and film.


    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 minimum fix in each fixer 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 that
    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 present in
    the "high tech" emulsions is resistant to fixation, and
    exceedingly insoluble.

    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) and when the halide is fully dissolved,
    the dye is removed.

    In some instances, the dye can be removed by treatment with hypo-
    clear, which usually contains 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 dilutions vary between
    paper and film fixers, and the "sudden" accumulation of
    iodide after developing films may greatly prolong paper fixation or
    leave insoluble silver iodide behind.

    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 fixer bath, rinsed and held in
    water, then fixed in the second fixer bath at the end of a session.
    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 fixer two baths. The RC time
    is optimistic, though five minutes per fixer 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 (hours).

    In any case, paper and film should be promptly removed from the
    second fixer , rinsed, and placed in a water fixer 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 fixer bath 1 of a fixer two fixer
    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 fixer bath commercial processing. The only advantage of rapid
    fix with film is decreased processing time and perhaps, decreased
    rinse time.


    Hardeners:

    For film, a hardening fixer is often preferred to minimize any
    emulsion damage in handling and to avoid reticulation. Very alkaline
    developers can remove the manufacturer's hardeners. If the emulsion
    is loaded with salts such as fixer , and placed in plain water, the
    emulsion can swell markedly due to water uptake in the emulsion due
    to osmotic pressure. If the water is warm, the emulsion may ripple on
    the surface, giving the alligator pattern associated with
    reticulation.

    Non-hardening fixers are often 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 which can speed wash times.

    If one wishes to remove hardener for toning, the following treatments
    may be used: 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.

    An exception to the rapid fix recomendation is Agfa Portriga paper
    which has a soft emulsion. If it is sepia toned (basic toner removes
    hardeners), emulsion damage may occur if the paper is heat dried.
    Therefore it should be hardened after toning. If fibers from a canvas
    mat drier or blotters stick to the emulsion, you may have that
    problem even with other papers. Kodak makes a separate hardener,
    however, I find the hardener offered by Sprint to be effective and
    economical. I also use it with their rapid fixer .


    Common Fixer Tests:

    Tests for fixer exhaustion which rely on precipitation of silver
    iodide aren't sensitive enough to determine whether a fixer is in the
    "archival" range or "commercial" range, and in
    some cases, whether the fixer is near exhaustion. Relying on that
    type of test with one-fixer bath fixation invites future disaster.

    Likewise, tests of wash water for fixer can't detect insoluble
    complexes of fixer in the paper or unfixed silver halide in the
    emulsion. Sulfide or selenium toner tests for silver in paper don't
    measure the insoluble complex (I) or degradation complexes, nor does
    silver nitrate react with those complexes. Some tests may be better
    than none and any warnings should be heeded, but in this instance,
    they may give a false sense of security if the results are false
    negatives.

    Follow the tables given by Haist (above), and reduce capacities by
    1/2 for TMax and other high tech emulsions.


    Hypo-clear and Eliminator:

    Usually, the removal of fixer and its complexes from film is fairly
    straightforward. With or without hypo-clear, the hypo and complexes
    diffuse out of the emulsion with washing, and aren't tightly bound.
    The potassium alum used as a hardener may complex small amounts of
    hypo and silver complexes, but that doesn't seem to occur with chrome
    alum. However, chrome alum isn't used in commercial products, and
    probably should be avoided for environmental reasons and staining
    problems.

    With papers, additional problems can arise due to the nature of the
    support. Some of the hypo and complexes are adsorbed to the baryta
    layer, fixer always penetrates the interstices between fibers of
    fiber-base papers, and with prolonged fixing (over 15-30 minutes),
    hypo and complexes can enter the fiber "cells", from which
    it is very difficult to remove. However, this does not occur with
    reasonable fixing times of 5 to 10 minutes.

    The hypoclearing properties of saline solutions was discovered by Dr.
    Bannow in 1889, but he used a 10% sodium chloride solution (100,000
    ppm) with rinses with moderate success. In 1903, Dr. Bayssellanee
    found that sea water was more effective, and used 30,000 ppm sea salt
    with 1 hour soaks followed by washes to remove salt (so much for the
    "US Navy discovery" myth).

    Although it was noted that film and paper washed in sea water (3%
    salts of which 2.6% is sodium chloride) lost fixer much more rapidly
    than washing in tap water (65% faster for film; 80-90% faster for
    paper), using table salt or sea salt as a clearing agent isn't a good
    idea. Removal of chloride was required, since chloride resulted in
    faster degradation of any residual hypo in the emulsion (note: the
    seawater use was for rapid processing and conservation of fresh
    water, not archival stability).

    Subsequently other hypo-clearing agents were examined, and polyvalent
    anions were found to be most effective in displacing silver. Of the
    group, 2% sodium sulfite buffered to pH 7.0 was found to be most
    effective. EDTA or other chelating agents may be included to remove
    calcium sulfite which can precipitate in/on emulsions.

    Although some suppliers indicate that a short soak in hypo-clear (1
    min) after fixing followed by a short wash time is adequate, rinsing
    films and papers before a 10 minute hypoclearing agent treatment
    works better, and prolongs hypo-clear life.

    Hypo-Eliminators

    Hypo-eliminators rely on the use of an oxidant such as peroxide to
    rapidly oxidize any residual hypo complexes in the film, preventing
    the reaction with image silver which would occur if they were
    permitted to degrade. Kodak HE-1 is a dilute mixture of peroxide and
    ammonia made up when used (never kept in an enclosed container) which
    oxidizes such complexes. However, it has been noted that oxidation is
    incomplete unless bromide is added to speed the reactions.

    In the "Craft of Photography" Vestal mentions that some
    studies indicated that HE-1 treatment wasn't as "archival"
    as supposed, and that a small amount of thiosulfate might stabilize
    the image. The point was clarified at a subsequent conference
    reported by Vestal. The topic is considered below (RC papers and
    stability).

    The current concensus seems to indicate that hypo-eliminators should
    not be used unless the image is subsequently toned with selenium or
    sulfur (sepia), or treated with Agfa's Sistan (thiocyanate).


    The Ilford Story:

    Coinciding with the introduction of Galerie paper, Ilford decided to
    introduce a quick 20 minute archival processing procedure. After
    development and stop, paper was to be fixed for 30 seconds in film
    strength rapid fixer , followed by a five minute wash, 10 minute soak
    in a wash aid, and another 5 minute wash.

    Later, the recommended fixing time was extended to 1 minute with
    little fanfare. If the wash aid isn't used, Ilford recommends a wash
    time of at least one hour. The precautions mentioned include good
    agitation, and use of fixer which hasn't approached its capacity. The
    "theory" is that silver removal from the emulsion is faster
    than accumulation in paper interstices, so supposedly little
    accumulation occurs.

    There are some problems.

    The procedure does _not_ work with Kodak papers and others which
    require longer fixing times. (Elite is a prime example.)

    Also, the retention of complex I in the paper isn't addressed or
    tested for, and complete non-image silver removal isn't checked.

    Ilford recommends one fixer bath rapid fixation. A capacity of 40
    sheets of 8x10 paper per qt (160 per gal) is suggested when a wash
    aid is used with a single fixing fixer bath or when a fixer two
    fixer bath system is used (which negates the short fixing time
    rationale). However, the capacity is reduced to 10 sheets per qt (40
    per gal) using a regular wash and single fixer bath fix.

    That disparity in capacities suggests that Ilford is relying on the
    wash aid to extend so-called fixer capacity when a single fixer
    bath is used. The implication is that for the 30 sheet difference
    between use and non-use of wash aid, significant insoluble complexes
    are carried over (see the Haist table). Note that Ilford's capacities
    for single fixer bath fixing are greater than Haist's
    recommendation for commercial processing (Ilford uses 2 g/l with wash
    aid or 0.5 g/l without). Their rapid fix might have a slightly
    greater capacity, but it is unlikely that silver levels are as low as
    Haist's _archival_ standard when silver levels higher than Haist's
    limit for commercial processing are tolerated.

    In the current Ilford tech sheet on Galerie, they mention that the
    archival treatment with a 20 min wash results in 1/4 the level of
    hypo in the paper as a 5-10 minute fix with "normal"
    washing. Note that a wash aid wasn't used with the paper fixed 5 to
    10 minutes in the "comparison". Remember, wash aids can
    increase rate of fixer removal by 80-90% with papers. The comparison
    really isn't valid, and it appears that Ilford's only standard for
    archival processing is residual reactive (free) hypo levels, and not
    the target of absence of insoluble monoargentothiosulfate and silver
    halide.

    Toning

    I don't intend to cover this in any detail, other than to say that
    selenium or sepia toning is required to ensure image permance,
    especially if prints are displayed. Gelatin always retains some water
    which can dissolve atomospheric oxidizing gases such as ozone and
    nitrous oxides, which can bleach the image and permit silver
    migration.

    Toning in selenium (1:3 for color chage to 1:20 for permance with
    minimal tone effect), or sepia prevents the problem. Also, it is
    claimed that treatment with Agfa's Sistan protects the image, though
    I can't find data to support their contention.

    There are a number of arcane approaches to selenium toning. If Rapid
    Selenium Toner is exposed to hypo in an acidic environment (acid
    fixer ), the selenite will be reduced to colloidal or metallic
    selenium, and a red stain will result. To avoid that problem, rinse
    the paper after fixing, and dilute the Rapid Selenium Toner in a
    solution of 2% Kodalk (20 g/l) rather than water or hypoclearing
    agent. The dilute toner may be stored in a glass container until
    exhausted through use.


    Water Spots

    Water spots are caused by high salt or particulate concentrations in
    wash water, which dry onto/in the emulsion. If you have problems with
    water spots, then soak the negatives or RC prints in the following
    solution for a few minutes before hanging to dry (don't use a
    squeegee - water will run off):

    1 gal distilled water
    10 ml Photoflo
    100 ml 70% isopropanol (rubbing alcohol from a pharmacy - be sure
    that it doesn't contain anything else)

    The solution can be reused if it's filtered before returning it to
    the storage container.
     
  2. Thanks, Dan. Interesting stuff.
     
  3. I really do believe rapid fixer 3-5 minutes, with hardener, is all that need be done.
     
  4. Thanks for that, Dan. It's a very comprehensive explanantion of the chemistry. Very informative.
     
  5. I know Ilford reccommends a two stop bath for archival. I lean towards less use of the same fix, maybe, twice or so as opposed to two step fixing just to simplify things.
     
  6. Chris,

    You mean two stage fixing, not two stage stop bath...

    Hans,

    That's the whole point of the article: You have to **assure** that the fixer removed the monoargentomonothiosulate (one silver cation and one hypo anion): Two stage fixing **assures** the halide and monoargentomonothiosulate removal.

    The key point is that "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."

    Cheers!
    Dan
     
  7. Dan,

    It was Bob who mentioned two stop baths. Notwithstanding, having read that article yet again I shall adopt two-stage fixing for all future work.
     
  8. Ctein, in his book Post Exposure, found that Sistan does work as well as toning for image protection on RC paper, at least in the short term (a few years under bright light). See page 160.
     
  9. How would two-step fixing apply to single use chemistry and processing in a Jobo? Just put another dose of fixer in the tank after the first fixer bath? That would bring the total steps to nine with three done outside the machine.
     
  10. Also, taco boy mentioned something about the 'clearing' of film. Is this when the film is no longer light-sensitive?
     
  11. Noelle, I just saw your two posts here.

    If you're using chemistry in a single shot manner in your Jobo, what you do is make up double the volume of fixer, and save the second fixer liquid to reuse for the next batch's first fixer bath.

    The whole idea is that 98% of the fixing is done in the first fixer bath; but that last couple percent of fixing can only be accomplished by using fresh fixer.

    Since C-41 fixer is $32.50 for 25 gallons (5 gallon cubetainer); and since it works for everything, there's No Excuse for underfixed film!
     

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