Free HCA?

Discussion in 'Darkroom Developing and Printing' started by David Nebenzahl, Oct 27, 2006.

  1. Just occurred to me: why can't people like me, who live near an ocean,
    just go there and, say, fill a 5-gallon container with seawater every so
    often to use as HCA?

    After all, that's how this property was discovered in the first place,
    wasn't it? Story goes that photogs processing prints on board military
    ships discovered the hypo-removing properties of salt water.

    Just as McDonald's is where you go when you're hungry but don't really
    care about the quality of your food, Wikipedia is where you go when
    you're curious but don't really care about the quality of your knowledge.

    - Matthew White's WikiWatch (
    David Nebenzahl, Oct 27, 2006
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  2. You could always pin some FB prints to a surf board and have some fun riding
    the waves.
    I agree, Burger King is much better.
    Foto`s in Monochrome, Oct 27, 2006
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  3. David Nebenzahl

    Tom Phillips Guest

    You'd probably need to be very careful to wash
    out the sea water, since it contains a lot of
    other substances besides salt. Sodium sulfite at
    2% solution was found to be more effective than
    most other salts but there are reasons to use
    a prepared HCA like Kodak's. One, it's balanced
    to a neutral ph which is above the isoelectric
    point of the film so the swelling of the gelatin
    is minimized. This helps the process of diffusion
    washing (the sulfite works via ion exchange but
    with a less swollen print or film diffusion
    washing is more efficacious.) Two, if you use a
    hardener for prints or film it preserves the
    Tom Phillips, Oct 27, 2006
  4. David Nebenzahl

    dan.c.quinn Guest

    Agfa went out of business still recommending
    2% sodium carbonate. I wonder if KRST's compatibility
    with the buffered KHCA had anything to do with their selection
    of sodium sulfite as a base for their hca? Both products were
    new to the market I'd guess about the same time; 1950s.
    Kodak told Ansel Adams, person to person, that the
    two could be mixed togeather. I take it that was
    not for general consumption. Not yet at least.
    The swelling is minimized at the isoelectric point.
    That ph is 5 +/- .2 or .3. Likely too low to work with KRST.
    That is not correct. Relative to how much watered
    the emulsion can be the emulsion holds scarce little
    at the isoelectric ph. As the ph increases the emulsion
    becomes more fluid; thined. The increase in swell
    does work against. Besides ...

    Within seconds of the wash the emulsion has the
    ph of the water. The ph of the hca has no effect upon
    the water or speed of washing. Emulsions come clean
    quicker because of the action taken within the hca.
    A high ph hca will speed hypo clearing. Carbonate
    vs unbufferd sulfite? I'd score one for Agfa;
    perhaps no faster but does not oxidize.

    Two factors speed all photographic processes;
    increases in ph and increases in temperature. Dan
    dan.c.quinn, Oct 28, 2006
  5. David Nebenzahl

    Tom Phillips Guest

    A bad use of words on my part. In rechecking
    James what it actually says is 2% sodium sulfite
    was found to be "as effective as any." I assume
    this refers to salts of comparable effectiveness.
    I don't remember seeing this statement from Adams.
    Is there a page reference from his books? I would
    think that if both S. sulfite/carbonate could be
    mixed together KRST/carbonate HCA would also be
    My understanding is minimum swelling aids
    the diffusion washing of ions and one of
    the reasons of having a ph balanced near
    the isoelectric point is to, in part,
    minimize swelling.

    Relative to how much watered
    I would think the hca would, due to diffusion,
    have some effect effect on the water's ph. If
    you soak prints (paper base, not just gelatin
    emulsion) you need to change the water as the
    wash water becomes saturated, then as you
    progress the wash water becomes less and less
    saturated as washing nears completion.

    Emulsions come clean
    If you're refering to ion exchange, yes...
    To a point. Too much increase in temp causes
    swelling and reticulation...
    Tom Phillips, Oct 28, 2006
  6. David Nebenzahl

    darkroommike Guest

    Depends on where you get your seawater I guess, open ocean is less
    contaminated by heavy metals and biological nastiness that the stuff you
    would be able to "score" off the beach near a metro area. Water
    quality is much worse than in the 40's and 50's. (And look out for
    hypodermic syringes!)
    darkroommike, Oct 28, 2006
  7. darkroommike spake thus:
    I was thinking more along the lines of, say, below Half Moon Bay, rather
    than, say, Ocean Beach in the City.

    Actually, if I were serious about this, I'd probably check with the
    Surfrider Foundation ( to get the scoop on
    where the worst pollution is.

    Just as McDonald's is where you go when you're hungry but don't really
    care about the quality of your food, Wikipedia is where you go when
    you're curious but don't really care about the quality of your knowledge.

    - Matthew White's WikiWatch (
    David Nebenzahl, Oct 28, 2006
  8. David Nebenzahl

    dan.c.quinn Guest

    So, Na2S03 "as effective as any." And of the other
    salts tested there is no mention? I doubt Agfa chose
    Na2CO3 by chance.
    The 1983 edition of The Print, a footnote page 132-133.
    I got it back wards. Adams used KRST in KHCA which was
    apparently in it's early history the way to use KRST. Adams
    used an alkaline 2nd fix. Kodak told Adams he could use
    plain water with HIS KRST. That's my reading.
    A carbonated KRST would have a high ph. Maybe
    not a good thing to have.
    You are not using your common sense. The gelatine
    swells because it is becoming more fluid, more like water
    itself. Your understanding is based on the misconception
    that the thickness of the emulsion is the ONLY factor
    involved. It is a factor, a minor factor.
    In a nut shell the gelatine swells due to like charge
    repulsion, + or -, from the neutral isoelectric point. The
    attachment of H+ or OH- ions causes the minute to
    colloidal sized gelatine particles to separate.
    The greater the diviation from a ph of about
    5 the more the separation and the more
    fluid becomes the emulsion.
    The emulsion becomes more and more permeable.
    That is the Major factor, permeability.
    It should go with out saying but all this about the hca,
    it's ph and ion exchange, it's composition, and swell or
    lack there of, has nothing to do with the wash save for
    it's duration and the amount of water used. The wash
    is water at it's ph.
    A good rinse after hca is usual, should be. The
    amount of wash water is massive compared with the
    residual amount of hca present. Even if carbonate were
    used I doubt the change from the water's ph could be
    of any significance. Dan
    dan.c.quinn, Oct 29, 2006
  9. David Nebenzahl

    marika Guest

    that is cute
    marika, Oct 29, 2006
    Richard Knoppow, Oct 29, 2006
  11. The use of sea water for washing dates back perhaps a
    century. Sea water was used on board ship and other places
    where fresh water was at a premium during WW-2. Research
    into the effects of various salts on washing, however, dates
    to well before this time.
    The function of Kodak Hypo Clearing Agent is described in
    detail in a paper published by the Kodak Research Labs "The
    Effect of Salt Baths on Hypo and Silver Elimination" R. W.
    Henn, Nancy H. King, abd J. I. Crabtree _Photographic
    Engineering_ 1956, Vol.7, Nos. 3&4 p.153ff
    The authors investigated a number of salts, they found
    the most effective in accelerating wash rate was Sodium
    Sulfite at about a 2% concentration. They also investigated
    the effect of the treatment on emulsion hardness and other
    properties. They found that an optimum wash aid was obtained
    by buffering the pH of the sulfite bath to about neutral
    (pH-7). The commercial product also contains two
    sequestering agents, EDTA Tetra-Sodium salt and Sodium
    Citrate. There are for the purpose of eliminating sludging
    from minerals in the water the solution is mixed with or
    from Aluminum from hardened emulsions. If a bath is to be
    used a single time the sequestering agents are probably not
    Sea water will wash out hypo in about half the time of
    fresh water. However, the residual sea water must itself be
    thoroughly washed out because it contains halides and other
    substances which will cause rapid deterioration of the image
    if left behind. Nonetheless, the overall use of fresh water
    is significantly reduced. KHCA and similar Sulfite wash
    aides are more effective than a sea water wash.

    The list of citations includes a couple which may be of
    "Washing Films and Prints in Sea Water" G.T.Eaton and
    J.I.Crabtree, _Journal of the Society of Motion Picture
    Engineers_ v.42, p380-391 (1943) The bibliography of this
    paper includes some history of the process.
    "The Use of Alkalies as Hypo Eliminators" E.E.Jelley,
    _Journal of Photography_ v.72, 480-485 (1932)
    Richard Knoppow, Oct 29, 2006
  12. David Nebenzahl

    Tom Phillips Guest

    There's no reason to have used S. toner mixed
    with HCA, but it was a comon practice when I
    was in school many years ago. There's also
    little reason to use Adams method of a HCA bath
    after toning, since washing stops the toner. I
    fix, give a short wash, then use HCA before toning...

    I can't find any reference as to which HCA Adams
    used. He simply stated a HCA or Kodalk should be
    used after fixing and washing as a "pre toning
    bath." He then states toning requires an alkaline
    environment or staining can result. However, the
    only time I ever had staining using an acid fix
    was when using a hardener in the fix.
    no, I'm not thinking about the thickness.
    And yes I know why the emulsion swells...
    Well, in checking my archives I found this
    excerpt from one of Richard's posts on HCA
    and alkaline fix:

    Buffering [HCA] to neutral has two advantages over using a
    simple sulfite solution: it preserves hardening where that
    is desired; it places the gelatin close enough to its
    isoelectric point to minimise swelling thus resulting in the
    shortest diffusion path for the various ions which is its
    desired to wash out.
    But makes little difference. If you tray wash
    using water changes it would make little if any
    difference, and if you use a washer it would
    make little or no difference, Rinsing only
    removes surface solutions. I rinse my film but
    this does not shorten wash time or make washing
    more efficacious, since the time required to
    rinse is simply added to the wash time...
    Look at the process of washing. What occurs is
    the removal of contaminants from the emulsion
    or paper substrates by diffusion into the wash
    water. A point of equilibrium is soon reached
    and washing ceases to be efficacious _unless_
    fresh water is introduced. That's why even with
    tray washing you need several changes of water.
    Now I've never measured the ph of wash water to
    see when this equilibrium is reached but it would
    certainly depend on the number of film/prints
    being washed. The reason you need watwer chanegs
    is to avoid prints/wash water reaching the same ph...
    Tom Phillips, Oct 31, 2006
  13. David Nebenzahl

    Tom Phillips Guest

    FYI there's a reference from Kodak to washing
    with sea water in the out of print pub J-1
    Black and White Processing Using Kodak Chemicals:

    "Photographic products can be washed satisfactorily
    in sea water. In fact, sea water can remove [fixer]
    from film in 2/3 the time required by fresh water.
    It is extremely important that sea water salts be
    removed by a final 2-5 minute wash in fresh water
    or in desalinated water." p. 21.
    Tom Phillips, Oct 31, 2006
  14. Snipping here...
    This sounds about right although Eaton and Crabtree said
    1/2 the time normally recommended for the material in their
    old paper. The above is safer. They also said a 5 minute
    wash in fresh water would remove the residual sea water.
    Richard Knoppow, Oct 31, 2006
  15. Sea water is more effective for washing than fresh water
    but much less so that treating with Sulfite. Its probably
    about the same as treating with an alkaline bath of a
    carbonate. Sulfite has a specific ion exchange property that
    displaces the Thiosulfate-silver complexes as well as
    thiosulfate itself. This means it will clean up after hypo
    that is a little exhausted.
    Richard Knoppow, Oct 31, 2006
  16. All this was investigated in the 1930's and 1940's at
    Kodak Labs. They were able to coat paper at will and tested
    the retention of paper stock with no coatings, stock with
    just the Baryta coating, and complete papers with emulsion.
    The paper stock, as Ilford pointed out much later, tends to
    bind up thiosulfate by friction rather than a chemical bond.
    This much reduces the effectiveness of Sulfite wash aids on
    the _paper base_ of fiber prints although it still has some
    accelerating property. This is why the wash time required
    for double weight paper remains at 20 minutes while the thin
    paper emulsion probably washes out in 2 or 3 minutes. Film
    emulsion takes longer to wash because it is a lot thicker
    than paper emulsion. Note that when treated with wash aid
    film still takes 5 minutes to wash where _untreated_ RC
    paper takes only 4 minutes even when fixed in an acid fixer
    with white alum. I've not seen experimental wash times for
    RC treated with Sulfite but it may be less than one minute.
    The binding effects in the emulsion of either film or
    paper are:
    Acid condition of the emulsion. When the pH is lower than
    the isoelectric point of the emulsion the elecric charges
    tend to attract Thiosulfate ions and Silver-complex ions.
    Since the isoelectric point of most photographic gelatin is
    slightly on the acid side of neutral making it neutral or
    slightly alkaline reverses the charge condition causing the
    emulsion to repel the above mentioned ions. The other strong
    bining effect comes from the potassium aluminum sulfate
    (white alum or plain alum) used as a hardening agent in most
    photographic fixing baths. White alum appears to have a
    specific mordanting or chemical binding effect for
    Thiosulfate ions and silver complex ions. The mordanting
    effect takes place within certain pH limits. At neutral or
    alkaline pH the mordanting effect no longer takes place and
    the ions are released. Alkaline pH will also undo the cross
    linking caused by the hardener so the hardening is
    destroyed. At neutral pH the hardening effect is at least
    partially preserved.
    Many modern emulsions are hardened in manufacture
    sufficiently so that they do not need the auxilliary
    hardening of a hardening fixing bath. Since it is the
    hardener that requires the fixer to be acid eliminating it
    allows the use of a neutral or alkaline fixer. However, the
    acid of an acid fixing bath also serves to prevent carried
    over developer from becoming active. If a non-acid fixer is
    to be used the film or paper should be rinsed enough to
    remove the bulk of the developer.
    A note about Selenium toner and KHCA. Selenum toner can
    be used immediately after fixing. However, an excess of acid
    can cause an overall stain from precipitated elemental
    Selenium. This can be peach colored or even red. The effect
    does not always take place. By treting the print or film to
    be toned in a bath that neutralizes the acid this source of
    staining will be eliminated. Note that this staining is very
    unlikely when a print has been washed before toning. Gelatin
    really has no pH of its own and takes on the pH of the last
    bath its been in. There _is_ a preferred pH, namely the
    isoelectric point, however Gelatin is not like most
    substances which have a characteristic pH. Washed emulsion
    will probably be pretty close to neutral.
    For many years Kodak recommended a weak solution of Kodak
    Rapid Selenium Toner (KRST) for image protection. The toner
    was to be used at about 1:20. At this dilution it can be
    diluted with Kodak Hypo Clearing Agent (KHCA) to perform
    both wash aid and toner functions. It as discovered nearly
    20 years ago that _diluted_ KRST was not effective in
    protecting images against oxidation. Full toning, or near
    it, is still effective, but the old recommendations should
    be discarded. There is no good reason for diluting KRST with
    KHCA or another alkali and some reason no to do so. The use
    of KHCA as a diluent for stronger solutions of the toner
    were _never_ recommended.
    The use of KHCA _following_ toning may have some
    benificial effect on accelerating the wash time necessary
    because KHCA contains a large amount of Ammonium Thiosulfate
    (rapid fixer). The orignal idea was that a weak solution of
    toner could be used in combination with the wash aid in
    order to save having to do two washes. Since, if the purpose
    of the toner is image protection, the diluted toner is no
    longer desirable, a double wash is probably necessary. Weak
    KRST will still produce some image intensification and may
    be desirable for that function, but should not be relied
    upon for archival protection of the image.
    Current recommendations are to use a Polysulfide toner
    for protection since such toners affect all densities
    uniformly and can be used for partial toning and still
    provide protection to all areas of the image. The problem is
    that these toners usually result in greater change in image
    color or density than weak KRST. Kodak Brown Toner is a
    commercially available polysulfide toner but such toners are
    fairly easy to make.
    Someone mentioned the use of a sulfite bath as a "stop
    bath" for toning. I think there is come confusion between
    KRST and KBT here. KRST does not need such a bath but it can
    used profitably with KBT. While the handbooks suggest a very
    stong solution of Sulfite, around 10%, I've found that
    normal working solution KHCA works fine. The yellow stain is
    cleared in a few seconds and there appears to be no
    continuation of toning in the wash.
    Richard Knoppow, Oct 31, 2006
  17. David Nebenzahl

    Tom Phillips Guest

    The reference to Crabtree is the one cited
    in James, p. 454, about the use of sea water.
    FYI it's G.T. Eaton and J.I. Crabtree in the
    Journal of Soc. of Motion Picture Photographers
    [England]. 1943, v 40 p.380 (as near as I can
    decipher the cite syntax...)
    Tom Phillips, Oct 31, 2006
  18. David Nebenzahl

    Tom Phillips Guest

    Richard Knoppow wrote:

    snip a good deal...
    This is also my experience, except that
    when using a hardener fixing bath (such
    as F-5) a long wash is needed to prevent
    staining. When not using hardener staining
    is much less of an occurance when toning
    in selenium. So, I think it relates more to
    the alum than the acid, since I can tone
    immediately after fixing (plus water rinse)
    in A. Thio. minus hardener with no stain...
    Tom Phillips, Oct 31, 2006
  19. David Nebenzahl

    Tom Phillips Guest

    Just reader FYI current recommendations for
    selenium is 1:9 for minimum 3 minutes.
    Richard, I believe you mean that KRST
    contains A. Thio, in which case washing
    in HCA after toning might be of benefit.
    Tom Phillips, Oct 31, 2006
  20. This was told to me in a conversation (or maybe it was
    e-mail) by Douglas Nishimura of the Image Permanence
    Institute quite some time ago. It is the minimum for image
    protection. However, it will cause a noticable change in
    image color or density on most materials. This is a general
    recommendation, not one aimed at microfilm where the
    original problem occured. For microfilm the current
    recommendations are toning is a Polysulfide toner like Kodak
    Brown Toner, Kodak T-8, or any of several published formulas
    such as IPI Silver Lock. The degree of toning is tested by
    bleaching out the silver using a Potassium Dichromate bleach
    and measuring the density of the remaning toned material.
    The density after bleaching should be on the order of 60% or
    more of the density before bleaching. This applies
    specifically to microfilm. However, the effectiveness of the
    toner can be tested in the same way for other materials.
    Note that the color shift caused by Polysulfide toner varies
    with different emulsions. For microfilm the shift is toward
    blue rather than the Sepia one would expect. The toned color
    has to do with the morphology of the original silver
    The other toning method recommended for microfilm is Gold
    toning, especially using Kodak GP-2. This toner is also
    suitable for pictorial negatives and prints but is quite
    Note that _any_ sulfiding toner produces very permanent
    images provided enough of the image silver is toned. Silver
    Selenide is just as stable as Silver Sulfide, the
    shortcoming of KRST being split toning when partial toning
    in high dilutions is used. Complete toning, or near it, will
    produce permanent images with a high degree of resistance to
    Note also that oxidation from atmospheric polutants has
    become a more important cause of image degration in the
    recent past than the traditional problems from uncontrolled
    sulfiding due to incomplete fixation or poor washing. In
    fact, very well fixed and washed emulsion is quite
    vulnerable to oxidation if not treated in a suitable toner
    or stabilizing agent.
    I point out that the popularity of highly diluted KRST
    was due to the idea that it could produce substantial
    protection against oxidation wityout causing a significant
    change in image color or density. It appears now that no
    toner will provide this condition. There are stabilizers,
    like the late, lamented Agfa Sistan, that can yield
    considerable protection with no change in the image, but
    they are not as effective as toning. Nonetheless, a
    stabilizer like Sistan or Fuji Ag-Guard (evidently not
    available outside of Japan) can be a good choice where no
    change is wanted in the appearance of a print or negative.
    Prints to be displayed should always be treated in a toner
    or stabilizer because of the increased exposure to oxidizing

    Sorry mistyped... I did mean KRST.
    Richard Knoppow, Oct 31, 2006
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