Not using a stop bath when developing film?

Discussion in 'Darkroom Developing and Printing' started by Andrew McCall, Nov 11, 2004.

  1. Hi Folks,

    The college I go to have recently decided not to use a stop bath when
    developing film as the gasses it produces seems to agitate some students
    with asthma.

    Can anyone tell me why it would do this to the asthma suffers, ie. what
    gasses are given off by the stop bath?

    What are the effects on processing when skipping the stop bath? We are
    using relatively slow developers like Agfa Rodinal and Ilford Ilfotec DD-X.

    I will probably be developing my film at home now, but I was wondering
    if I have to, will developing at college with no stop bath have an
    effect on my negatives.


    Andrew McCall
    Andrew McCall, Nov 11, 2004
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  2. Stop bath is a mild solution of Acetic acid, about half
    the strength of white vinegar. It can react with the sodium
    sulfite in developers to release a small amount of Sulfur
    dioxide gas. Sulfur dioxide has a sharp odor and can trigger
    asthma in those afflicted. It can also release Carbon
    dioxide gas when developers with carbonates are used. There
    are very few current packaged film developers with carbonate
    in them but most paper developers have it. Carbon dioxide in
    these very small amounts is not dangerous or irritating. Nor
    will it cause pin-holes in modern emulsions.
    Stop bath is important in stopping development at a
    definite point but a plain water stop can be used provided
    its thorough. It should really be a short wash. Thoroughly
    agitate the film in the water for a minute or more.
    Carried over developer will react with the acid in the
    fixing bath the same way it does with the stop bath.
    Generally, acid fixing baths do emmit some sulphur dioxide
    The use of a non hardening fixing bath or a neutral bath
    will eliminate this. Kodak Rapid Fixer with Hardener is
    reasonably low odor if the hardener is not added. Agfa
    Universal Fixer, used in color processes, is a neutral pH
    non-hardening rapid fixer.
    Odor free stop baths can be made using Citric acid and
    Sodium bisulfite or metabisulfite. Citric acid stop baths
    should not be used with hardening fixing baths because the
    citric acid tends to cause precipitation of the alum
    hardener. Ilford packaged stop bath concentrate is made from
    citric acid but citric is also available cheaply from health
    food stores and for use in home canning. Use about 15 grams
    per liter for stop bath. This is also about the right amount
    of Sodium Bisulfite or metabisulfite. Most Sodium bisulfite
    is actually metabisulfite, they are identical in action in
    photo solutions.
    Good ventillation is a necessity for a darkroom.
    Richard Knoppow, Nov 11, 2004
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  3. nov1104 from Lloyd Erlick,

    Using plain tap water in place of an acid stop bath is
    common practice. It requires a certain care, but is
    easy and effective.

    Personally, I used to enjoy the smell of stop bath. I
    still like vinegar on my french fries. But eight or ten
    hours around stop bath, many times, has made me hate
    all smells in my darkroom. I like an odor free darkroom

    My website has articles about my quest for a smell free
    zone in my darkroom. The one about non-acid print
    processing might be of interest (applies to film, too,
    more or less.) Look under 'technical' in the table of

    Lloyd Erlick Portraits, Toronto.
    voice: 416-686-0326
    Lloyd Usenet-Erlick, Nov 11, 2004
  4. Andrew McCall

    The Wogster Guest

    Ilford makes a odorless stopbath, which I think is based on citric acid
    rather then acetic acid. Technically you still have a stop bath, it's
    just water instead of a diluted vinegar. What I usually did was double
    the length of the stop, and then reduce the capacity of the fixer to
    half. I never used a stop bath with film, but 3 20 second water soaks,
    and then used the fixer 1 shot. Never had a problem.

    The Wogster, Nov 11, 2004
  5. Andrew McCall

    Mike King Guest

    My own practice is to use a water rinse when processing film between the
    developer and fix, since this is one-shot it will stop development almost as
    effectively as an acid stop.

    For printing in trays, developer carry-over will render a water stop bath
    alkaline in short order at which point you are no longer stopping
    development but doing stand development in a two bath developer! Did this
    by accident one time (diluted Dektol stock 1+31 in my stop bath tray instead
    of acetic acid--really tired that night) and got some interesting results,
    if you leave prints in the diluted "stop" tray for extended periods of time,
    sort of Sabattier but weak and orange-ish highlights, standard practice in
    this darkroom was to let prints pile up in the stop bath and then fix them
    in batches before moving out of the darkroom to the big Pako Washer.
    Mike King, Nov 11, 2004
  6. The use of a stop bath is really not needed for film, in fact there have
    been "monobath" (combined developer/fixer) products on the market and
    Edwal used to include instructions on how to use their developers
    as monobaths.

    The main reason to use one is to force development to end at a specific time
    so that the results are the same, but using the same rinse procedure will
    each time do the same thing (with slightly different results).

    It's also to keep the alkeline developer from mixing with the acid fixer.
    The acid in the fixer acts as an emulsion hardner. Some fixers include
    it, some include it as an option (remember the two bottle kodak rapid
    fixer with hardner?) and some don't have it at all.

    Geoffrey S. Mendelson, Nov 11, 2004
  7. I will probably be developing my film at home now, but I was wondering

    try this healthy combination:
    rinse your film for about 60" in plain water.
    It's ok, and it's what I do.
    Never needed stop bath.

    stefano bramato, Nov 11, 2004
  8. Its not the acid in the fixing bath that does the
    hardening. Common fixing baths use Potassium aluminum
    sulfate, also known as White Alum, or just Alum. The alum
    hardens the gelatin but works only over a fairly narrow
    range of pH. The hardening remains at neutral pH but is
    destroyed at much on the alkaline side of neutral. There are
    other hardeners, mostly organic compounds, which are
    effective hardeners in alkaline solution. These are common
    in color processing.
    Because the acid in an acid fixing bath reacts with the
    thiosulfate and eventually decomposes it some means must be
    provided to protect the thiosulfate. This is usually sodium
    sulfite. The large amount of sulfite needed also tends to
    prevent stains from the reaction products of carried over
    Because modern stop baths were devised to work with or
    without a stop bath they are heavily buffered by using a
    combination of Acetic acid and Boric acid. This tends to
    keep the pH of the bath in the right range for effective
    hardening despite carried over developer or carried over
    stop bath. This type of bath also tends to have less problem
    from sludging of the hardener when the pH is off the right
    It should be noted that the ability of thiosulfate to fix
    is independant of pH.
    The odor from fixing baths is due to some decomposition
    of the thiosufate by the acid. Making the bath less acid
    will reduce the odor. Neutral fixing baths, essentially just
    thiosulfate and sulfite, are very low odor.
    Citric acid or sodium bisulfite or sodium metabisulfite
    can be used for odorless stop baths. Citric acid is not
    ideal for use with fixers using alum hardeners because it is
    a sequestering agent for aluminum and will cause reduction
    of hardening and may also cause sludging.
    Many modern films do not require hardening so do not need
    fixers which are acid. I seen no advantage whatever in
    making a fixing bath alkaline but making neutral fixer is
    fine. Also, the swelling of the emulsion will be less in a
    neutral bath than in either an acid or alkaline bath.
    There is an advantage in washing if the emulsion is
    neutral when it it is washed. If an acid hardening fixer is
    used a buffered sulfite wash aid, like Kodak Hypo Clearing
    Agent, will adjust the pH to neutral and also eliminate the
    binding effect of the alum on thiosulfate and fixer reaction
    products. Wash times when the emulsion is treated in such a
    bath are the same regardless of the type of fixing bath
    used. In addition the sulfite acts as an ion exchanger for
    thiosulfate so the wash is very much accelerated over what
    one would have from a simple neutralizing bath without
    I still think acid stop baths prevent more problems than
    they cause but certainly a plain water rinse works if it
    actually washes out the bulk of the developer.
    BTW, someone mentioned monobath processing. Much of the
    research on this was done by Grant Haist. He wrote a small
    book called _The Monobath Manual_ (very hard to obtain now)
    and also covers monobaths in his _Modern Photographic
    Processing_. Monobaths are not simply a mixture of developer
    and fixer. They must be very carefully formulated and
    matched to a specific emulsion. They have some very
    interesting properties, not least of which is very
    considerable immunity to temperature and time variations.
    Haist shows some examples suggesting the possible image
    quality is very high. For some reason monobaths have never
    become popular except for some special rapid access uses.
    Richard Knoppow, Nov 13, 2004
  9. Andrew McCall

    John Guest

    On Sat, 13 Nov 2004 03:27:18 -0800, "Richard Knoppow"


    Great post as usual.

    Perhaps you meant "fixing baths" ?
    I think it's just as you indicated that they need to be
    formulated for specific films and I would add that those formulas were
    used one-shot and probably had limited stability due to the high
    alkalinity. The formulas that I'm familiar with use hydroxide as an
    accelerator. Perhaps there are other agents used ?


    John S. Douglas, Photographer -
    Please remove the "_" when replying via email
    John, Nov 13, 2004
  10. Andrew McCall

    Tom Phillips Guest

    yeah I think he should consider adding a regular
    joke line to his sig :) Who knew?

    Unless one _is_ alkaline I'd use a stop.
    Tom Phillips, Nov 13, 2004
  11. Andrew McCall

    Dan Quinn Guest

    Now days the integrity of incorporated hardeners is more of
    a concern. Most B&W processing is done without hardeners added
    to the chemistry.
    Developers can be very alkaline. Have you any idea just how
    alkaline they can be and not degrade the film's or paper's
    incorporated hardener?
    I've a notion that most films and papers are pre-process
    hardened as fully as any in-process hardener will do, even more
    so. Is that notion correct?
    Perhaps pre-process hardening is less than if there were none
    and the hardening left to an in-process hardener. Maybe a
    combination of the two would result in the most hardened
    emulsion possible. What do you think? Dan
    Dan Quinn, Nov 13, 2004

  12. Of course, I meant fixing bath although buffered stop baths are
    also possible and will have a longer life than a plain acetic or
    citric acid bath.
    Grant Haist goes quite deeply into monobaths, evidently this was a
    subject of his research work at Kodak. Many monobaths do use sodium
    hydroxide as the accelerator, the reason is simple: the developer must
    compete with the fixer. Development must be completed before enough of
    he halide is removed to destroy the image. Monobaths must also contain
    a hardener. Haist has formulas with Glutaraldehyde but also lists a
    number of oganic hardeners suitable for use in highly alkaline baths.
    In both of his books Haist shows formulas optimized for Tri-X (roll
    film) and Verichrome Pan, I think a couple of others but I am away
    from my books at the moment. At least a couple of these formulas
    include Phenidone as a primary developing agent.
    I should point out that the hardener in fixing baths was intended
    to compensate for the swelling caused by both the alkaline developer
    and the acid fixer. Auxilliary hardeners are less necessary where the
    pH of the solutions does not vary from neutral by much. Eliminating
    the stop bath is attractive but there is still the problem of stopping
    the development quickly and keeping developer from carrying over to a
    neutral or alkaline fixing bath where it can continue development. A
    long rinse in running water seems to be the solution. This is the
    method used in alkaline color processing. Rinses are typically 1 to 3
    Where highly alkaline developers are used, such as lithographic
    developers, it is common practice to use an anti-swelling stop bath.
    Typically this has about 15 grams/liter of Sodium sulfate in it
    (sulfate not sulfite). Sulfate is also used in tropical developers to
    reduce emulsion swelling and slow the rate of development. Since many
    B&W films, for instance T-Max, are now made to withstand 100F
    processing such measures are not necessary for them. However, films
    like Tri-X are still relatively sensitive to emulsion swelling. It was
    also common in tropical processing and lith processing to use a
    chrome-alum stop bath. Chrome alum is acid and is a very effective
    hardener. However, it must operate at very low pH (around 2.0) so is
    difficult to incorporate into fixing baths although there are chrome
    alum fixing baths. Its use is probably not necessary for any film
    these days.
    With all the talk about alkaline processing and eliminating stop
    baths it seems to have gotten lost that this procedure has been used
    with completely satisfactory results for many decades. The proper use
    of an acid stop bath stops development quickly and prevents carryover
    of active developer into the fixing bath. It also prevents the
    possible generation of developer stain where it is allowed to continue
    in a bath without sulfite.
    It also seems to me than in reading the reasons for not using acid
    stop baths I am really seeing complaints of problems from bad
    practice. Even complaints about odor can be solved by using acids
    other than Acetic acid.
    Pin holes are extremely unlikely to be caused by any conventional
    packaged developer or fixer. For one thing modern emulsions are not
    very vulnerable to it and very few current film developers use
    carbonate, the villan in outgassing. A pinhole is an actual disruption
    of the emulsion. I suspect that very often what people are seeing are
    small clear spots caused by dust on the negative. Pin holes CAN occur
    because of coating problems. These exist in the emulsion from the
    manufacturer. A very great deal of research and technical development
    has gone into making very consistent coatings. This is very well
    established technology but even the best manufacturers may have
    problems especially in these days of low sales and cost cutting.
    Personally, I suspect the whole movement to use alkaline processing
    is a sort of belief in black magic. Well, folks, there just isn't any
    black magic in photographic chemistry anymore. Even emulsion making,
    once one of the most closely guarded proprietary secrets in any
    industry, are now public record and anyone who is willing to do some
    research, AND has a decent understanding of organic and colloid
    chemistry, can find out how its done.
    Now, watch the flames come:)

    Richard Knoppow
    Los Angeles, CA, USA
    Richard Knoppow, Nov 14, 2004
  13. 1. A test performed in 1966 by Popular Photography magazine showed NO
    difference between the grain of Tri-X processed with or without a stop
    bath, magnified under a microscope.

    2. I quit using stop bath because I don't think it is the best way to
    stop development evenly. For about 10 years now I simply pour several
    large containers of tempered water into my Paterson tanks and flush
    the developer out. I never have streaks anymore, which I sometimes
    experienced with stop bath.
    Uranium Committee, Nov 14, 2004
  14. Andrew McCall

    John Guest

    Doggone it ! Ansel beat me to all that Black Magic developer


    John S. Douglas, Photographer -
    Please remove the "_" when replying via email
    John, Nov 15, 2004
  15. Andrew McCall

    Dan Quinn Guest

    RE: (Uranium Committee) wrote
    Eddie Ephraums has suggested a water rinse prior to an acid
    stop. IIRC, his concern is with reticulation. Of course the rinse
    will remove some developer, and dilute and neutralize that which
    remains. Short acid stops are recommended by Ilford and Kodak.
    They will confer upon and to some small extent within the
    emulsion the acidity needed to maintain the acid fix.
    I've been reviewing Dr. Gudzinowicz's evaluation of water vs
    acid "stops". Of course he goes on and on some what. Search this
    NG for, 3.8 4.8 5.8 pka to assess at least one treatise
    of his on that subject and associated matters. Dan
    Dan Quinn, Nov 15, 2004

  16. The problem as I see it is that when the stop bath hits the film in a
    tank it may do so unevenly, causing some streaking. I did occasionally
    experience this. By flushing the developer out with water under a
    little pressure or flow, one is assured of a kinder, gentler end to
    development. I simply leave the tank full of developer, and begin
    pouring water in through a funnel into the neck of the Paterson tank.
    This way, the water replaces the devloper, and the developer is not
    left clinging to the film in uneven layers, which can happen when the
    tank is emptied and allowed to drain before the next step. This
    developer clinging to the film can cause uneven development.

    This method may not work with stainless steel tanks, because there is
    no flow-through mechanism in them.

    The Paterson tank allows the solution to go down the center tube and
    fush out the sides.
    Uranium Committee, Nov 16, 2004
  17. Andrew McCall

    Tom Phillips Guest

    You must have been naked and hallucinating in your darkroom...
    Troll nonsense. Developer simply continues to develop
    until exhausted. Doesn't cause "uneven" development,
    since the negative density controls the effect. Also,
    with either a water rinse or an actual stop bath diffusion
    should occur at the same rate. Being acidic, stop bath works
    quicker by neutralizing developer _alkalinity_ and thus has
    the advantage of preventing carry over.
    Tom Phillips, Nov 17, 2004
  18. Uneven coating of developer will certainly cause streaking, as would
    occur when stop bath is splashed onto the film that still has areas
    that are wet with developer.
    I rinse the film thoroughly with lots of water that displaces and
    replaces the developer over about 7 seconds. The point is that the
    change-over is more uniform, because the water does not arrest
    development instantly, but smoothly.
    Uranium Committee, Nov 17, 2004
  19. Use water as a stop bath instead. While it doesn't
    neutralize the alkaline developer the way an acid
    stop does, the sudden sharp dilution of the developer
    has much the same effect.

    Or use a citric acid stop bath, instead of acetic acid.
    Acetic acid smells (vinegar). Citric acid doesn't.

    Laura Halliday VE7LDH "Que les nuages soient notre
    Grid: CN89mg pied a terre..."
    ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
    Laura Halliday, Nov 17, 2004
  20. Andrew McCall

    Tom Phillips Guest

    One does not "splash." One immerses.
    Sorry. Diffusion takes at least 30 seconds and the
    developer continues to be active in thin (less dense)
    areas of the negative. Development in the emulsion is
    not arrested ("smoothly" or any other way) by dilution,
    but simply continues to develop until exhausted.
    Tom Phillips, Nov 17, 2004
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