milkish and cloudy fixer

Discussion in 'B&W: Film, Paper, Chemistry' started by Alessandro Serrao, Aug 8, 2005.

  1. Alessandro Serrao

    Alessandro Serrao Member

    Messages:
    997
    Joined:
    Oct 20, 2004
    Location:
    Rome, Italy
    Shooter:
    35mm
    I'm preparing a normal fixer using:

    1) Water 500ml
    2) Sodium thiosulfate 120g
    3) Sodium sulfite 10g
    4) Sodium metabisulfite 25g

    to this solution I add 25ml/l (12.5ml) of Tetenal Harter (potassium alum based hardener). The minute I add this the fixer turns immediately milkish and cloudy.

    Why?
     
  2. Aggie

    Aggie Member

    Messages:
    4,925
    Joined:
    Jan 1, 2003
    Location:
    So. Utah
    Shooter:
    Multi Format
    Where do you live? You may have naturally occuring silver in the water. Park City Utah has a major problem with this. Try distilled water and see if that solves the problem.
     
  3. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format
    I have had occasion when adding alum hardner to rapid fixer (ammonium thiosulfate) the alum precipitates. This is usually due to not having the other ingredients completely dissolved and in solution.

    From what you describe, I would think that this may be the problem...if the water supply contained silver, I would think that the precipitation would occur before the hardner is added.
     
  4. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,779
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Alum precipitates immediately as a white cloudy material, if the solution has a pH value much above about 5.5.

    From your description, this is what is taking place. You can add some 28 % acetic acid to see if it redissolves, but I doubt that it will.

    The pH of an alum fix must be below 5.0 to work.

    PE
     
  5. Gerald Koch

    Gerald Koch Member

    Messages:
    1,670
    Joined:
    Dec 14, 2004
    Shooter:
    Multi Format
    The milkiness may be sulfurization caused by the solution becoming to acid when you add the hardener. Colloidal sulfur precipitates and cannot be redissolved. The 25 grams of sodium metabisulfite already makes the fixer quite acid and the hardener causes the pH to drop even lower.

    Most manufacturers are now recommending fixing baths without added hardener. This allows the thiosulfate to wash out more rapidly. This is especially true for FB papers where the alum holds the thiosulfate in the paper base.

    If you really think that you need hardener then halve the amount of meta-bisulfite in your formula and see if this helps. You may have to eliminate it entirely.

    When you add the hardener the fixer should be stirred rapidly to prevent local concentrations from becoming to too acid.
     
  6. Alessandro Serrao

    Alessandro Serrao Member

    Messages:
    997
    Joined:
    Oct 20, 2004
    Location:
    Rome, Italy
    Shooter:
    35mm

    So, being the role of metabisulfite, to acidify the fixer solution, and being the Tetenal Harter cointain a 28% acetic acid, I have to eliminate the metabisulfite entirely, is that correct?

    Unfortunately I haven't a pHmeter handy; I have to use the hardener because I use it in the b&w reversal process.

    Can I use the Tetenal harter alone, as a pre-bleach bath, to fight against the swelling of the gelatine in the following permanganate-based bleach bath?
     
  7. Gerald Koch

    Gerald Koch Member

    Messages:
    1,670
    Joined:
    Dec 14, 2004
    Shooter:
    Multi Format
    What is the composition of the bleach bath that you are using?
     
  8. Alessandro Serrao

    Alessandro Serrao Member

    Messages:
    997
    Joined:
    Oct 20, 2004
    Location:
    Rome, Italy
    Shooter:
    35mm
    The bleach I'm using is potassium permanganate acidified with bisulfate.
    In particular:

    Part A
    Potassium permanganate 4g
    Water to make 1l

    Part B
    Sodium bisulfate 66g
    Water to make 1l

    I mix 1:1 immediately before use.


    As a sidenote: on photo.net someone is suggesting me that: "No, no! The cloudiness you see is some kind of aluminum precipitate; it's because the pH is too HIGH. You need to lower the pH."

    I'm confused. :confused:
     
  9. Gerald Koch

    Gerald Koch Member

    Messages:
    1,670
    Joined:
    Dec 14, 2004
    Shooter:
    Multi Format
    There's no way that the pH can be too high with the combination of metabisulfite and the acetic acid in the hardener. Take my word as I am trained as a chemist.

    I really believe that you can omit the metabisulfite and use just the hardener.
     
  10. Alessandro Serrao

    Alessandro Serrao Member

    Messages:
    997
    Joined:
    Oct 20, 2004
    Location:
    Rome, Italy
    Shooter:
    35mm
    Since I'm perfectionist for nature I wanna understand well what's happening around me, especially in chemistry.
    Are you sure that the cloudy precipitate is colloidal sulfur (H2S) and not alluminium precipitate?
    Excuse me if I'm hammering you on this (insignificant point).
     
  11. dancqu

    dancqu Member

    Messages:
    3,676
    Joined:
    Sep 7, 2002
    Location:
    Willamette V
    Shooter:
    Medium Format
    Did you mean aluminum hydroxide? Dan
     
  12. Claire Senft

    Claire Senft Member

    Messages:
    3,242
    Joined:
    Dec 7, 2004
    Location:
    Milwaukee, W
    Shooter:
    35mm
    Does having the "milky" appearance interfer with the functioning, including hardening of the fixer?
     
  13. Gerald Koch

    Gerald Koch Member

    Messages:
    1,670
    Joined:
    Dec 14, 2004
    Shooter:
    Multi Format
    Aluminum hydroxide can only form at a pH well above 7. As I said your initial solutions is quite acidic due to the presence of the metabisulfite. You are then adding the hardener which contains acetic acid. When solutions of thiosulfate are made too acidic or when a local region of the solution becomes too acidic due to lack of stirring colloidal sulfur will come out of solution.

    Advantage of this reaction is taken in the making of hypo alum toner. A solution of sodium thiosulfate and potassium alum are mixed and heated. The alum being acidic itself causes some of the thiosulfate to decompose into various sulfur compounds and colloidal sulfur. Prints are placed in this bath to be toned brown.

    BTW, the decomposition of thiosulfate is the basis of a freshman chemistry demonstration called "The Setting Sun". A solution of sodium thiosulfate is set up with a slide projector behind the beaker shining on a movie screen. Acid is slowly added to the solution with stirring and what appears as an image of the sun slowly goes from white to yellow to orange and finally to dark red. This is caused by collodial sulfur scattering the light. As the particle size gets larger the light is scattered more resulting in the color shifting to red.
     
  14. Aggie

    Aggie Member

    Messages:
    4,925
    Joined:
    Jan 1, 2003
    Location:
    So. Utah
    Shooter:
    Multi Format
    Gerald another basic chem demo is taking water you boiled red cabbaage in to use as a universal indicator. It changes from clear to pink depending on the ph. At the end of the demo I use to do at grade schools in the SW, I would ask what they thought putting silver nitrate would do to the tap water we experimented with. I was surprised when I was doing the chem demo in Park City Utah, and the solution immediately turned milky and cloudy right out of the tap, without me adding any silver nitrate. Later I talked to one of the City Engineers, and he told me that the mines in the area have effected the water supply. That is when I started using bottled water religiously.

    I figured since This thread didn't indicate that it was precipatate, it had to be something similar to the cloudy milkiness you get from that experiment.
     
  15. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,779
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    The solution can be either too acidic or too alkaline.

    If too acidic, either the hypo will sulfurize and form colloidal sulfur with release of sulfur dioxide gas and hydrogen sulfide gas or if too alkaline the alum will precipitate as aluminum hydroxide. It is interesting to note that although the alum would be expected to precipitate at pH 7 or higher, I have observed it to ppt at as low a pH as about 6.0. It probably depends on the other ingredients salting it out. Aluminum salts are 'amphoteric' that is they can behave as either acidic or alkaline salts depending on the phase of the moon.

    The use of ammonium or sodium salts has no effect on alum precipitating nor on any propensity to sulfurize. Hypo is hypo (thiosulfate), sulfite is sulfite, and alum is alum regardless of the mix of sodium and ammonium ions present. The overriding factor here is probably pH.

    Just FYI, adjusting pH with sulfuric acid vs acetic acid at exactly the same concentration will give different results. The reason is that sulfuric acid is far more acidic at the same concentration than the same amount of acetic acid. Therefore, you are safe adjusting pH with acetic acid up to about 50% concentration whereas you would destroy your fix through sulfurization and release of sulfur dioxide gas at that concentration of sulfuric acid.

    The point being that aluminum Sulfite can be quite acidic. It is basically aluminum hydroxide dissolved in sulfuric acid. At least that is one way to look at it. Therefore, it can have a profound effect on pH if it is too concentrated. If the fix is too concentrated and too alkaline, it can suddenly swing the other way and become too alkaline.

    This is not a simple situation. Fix chemistry is quite complex.

    PE
     
  16. dancqu

    dancqu Member

    Messages:
    3,676
    Joined:
    Sep 7, 2002
    Location:
    Willamette V
    Shooter:
    Medium Format
    [QUOTES=Photo Engineer]

    "If too acidic, ... the hypo will sulfurize and form colloidal sulfur
    with release of sulfur dioxide gas and hydrogen sulfide gas ..."

    Both of which are highly soluble in water and may give no clue.
    I'm not so sure of H2S formation in that solution.

    "... or if too alkaline the alum will precipitate as aluminum hydroxide."

    That, at least from my reading, can be less than ph7.

    "...and alum is alum... The overriding factor here is probably pH."

    And in this case a potassium aluminum sulfate compound. Dan
     
  17. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,779
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Dan, the decomposition of hypo often leads to formation of H2S either through oxidation of acidification or both. The decomposition of sulfites to sulfur dioxide takes place with acidification. Both gases are sufficiently insoluable in the acidic hypo that the gas is given off in noticeable amounts.

    Both are toxic.

    Decomposition of alum hardening fixers at pH values over about 6 will lead to precipitates of aluminum hydroxide.

    PE
     
  18. Ryuji

    Ryuji Member

    Messages:
    1,416
    Joined:
    Jan 15, 2005
    Location:
    Boston, MA
    Shooter:
    Multi Format
    That fixer will have too high a pH to use alum hardener without an extra means of solubilizing alum. Old (pre WWII) alum hardening fixers have working pH of 4 to 4.5 to avoid this precipitation problem. In such a low pH range, the hardening effect is reduced, and the sulfurization becomes more serious problem after majority of bisulfite ions are oxidized. In modern alum hardening fixer, the solution contains agents that form soluble aluminium complex that also posseses hardening function. Classic work by Crabtree (or might it be Russell, I need to check) was to include boric acid in the fixing bath. There is a new patent assigned to Konica which uses alpha-hydroxyl acids and their derivatives for this function, allowing to formulate stable alum hardening fixer without using borates. With these agents, a practical alum hardening fixer can be formulated in the pH range of 5 to 6, but not much higher. Sludge will form above pH 6, even with boric acid. The hardening effect of alum is maximum at the highest pH that does not precipitate out insoluble aluminium salts. Therefore, good pH buffering is very important in optimal design of alum hardening fixers.

    I would recommend you to buy a hardening fixer, or study the history and chemistry of fixing baths from the original research reports (that is, not Anchell and Troop or anything like that). If you want to jump start, I suggest to find a decent Kodak formula that incorporates boric acid in addition to acetic and/or citric acid in the fixing bath as a starting point.

    I am pretty sure that the problem you have is not sulfurization. (Comments by Jerry Koch is irrelevant.) This is because sulfrization (acid decomposition of thiosulfate to form elemental sulfur) is very slow and almost insignificant within the pH range you are looking at, as long as bisulfite ions are not fully oxidized. You are seeing immediate precipitation after addition of alum solution. This is exactly what happens when the fixer's pH is too high in absence of borate (or another suitable agent) in the solution.

     
  19. snapguy

    snapguy Member

    Messages:
    1,297
    Joined:
    Jan 1, 2014
    Location:
    California d
    Shooter:
    35mm
    b and b

    Danged if I will drink and Bourbon and Branch in youse guys' neighborhoods.
     
  20. Bill Burk

    Bill Burk Subscriber

    Messages:
    4,984
    Joined:
    Feb 9, 2010
    Shooter:
    4x5 Format
    Does it has any effect on the process?

    I mixed some fix and it became milky today. It wasn't the good stuff since a shop I get supplies from didn't have my usual. I dipped a leader in to see time to clear. It cleared in a reasonable time... But I swear it looked like I'd soaked my film in a mud bath, it was covered with crud that wouldn't easily rinse off. So I didn't use it, and grabbed a new box of Kodak fix.
     
  21. Xmas

    Xmas Member

    Messages:
    6,454
    Joined:
    Sep 4, 2006
    Location:
    UK
    Shooter:
    35mm RF
    colloidal sulphur (S)...
     
  22. Rudeofus

    Rudeofus Subscriber

    Messages:
    2,569
    Joined:
    Aug 13, 2009
    Shooter:
    Medium Format
    Add similar amounts of washing soda and Sodium Sulfite until the cloudiness is gone (warning: slow process!). Start with 10 g/l of each. Do a clip clearing test before you use the fixed fixer, and throw it out if clearing time is excessive.
     
  23. pen s

    pen s Member

    Messages:
    241
    Joined:
    Sep 24, 2011
    Location:
    Olympia, wa.
    Shooter:
    35mm
    I started another thread about 'milky fixer' yesterday. Didn't do due diligence (say that ten times fast) and a simple search before I posted.

    What I described as 'milky' was more a slight haze, a not quite clear appearence to the solution. But, since it cleared the film, and left no residue, all within a normal time, I decided to hold judgement. This morning I rechecked the solution and the hazy apperence is still there. There are also a few, very few, very small white bits floating on the top. They are not dispersed throughout the solution. After reading this thread it looks like I should source some PH strips and actually test the fixer as mixed.

    About 25% into the nominal life of my film fixer I start to get a black precipitate in the solution. I assumed this was a silver salt of some type and just filter it out before use. I have always used fixer according to manfactures instructions in regard to number of films that can be fixed and have never ran into excessive fixing times so I suspect they are conservative in their numbers.
     
  24. Jim Noel

    Jim Noel Member

    Messages:
    2,144
    Joined:
    Mar 6, 2005
    Shooter:
    Large Format
    Since most modern films are pre-hardened, why use hardener? Non-hardening fixers are also preferred for papers, especially if toning is in the offing.