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  1. #61

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    Quote Originally Posted by Photo Engineer View Post
    Dan; I say again! This dilute fixer must maintain
    the silver complex solubility during the early stages
    of washing. PE
    Although the fixers I use are very dilute they are not so
    dilute as the fixers retained by a print or film which has
    had a post-fix rinse-hca treatment. That is, at the earliest
    stage of washing the retained fixer is less when the usual
    post-fix procedures are employed.

    A post fix in wash precipitation of silver halide I'd think
    more a worry with the usual processing procedure. Few
    I believe move prints directly from fixer to wash. I'm one
    of the few. That is due to the one-shot nature of a very
    dilute fix; one or a few at same time processed. The
    fixer once used goes down the drain. Any home
    brew or off the shelf fixer will do.

    I don't worry about post-fix silver halide precipitation.
    I've tested with fixers so dilute as to not clear, film
    and paper. With correct amounts I've not noticed
    any problems. Zero stains using Kodak's and
    Ilford's formula HT-2 and the ST-1 test. Dan

  2. #62
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    Some advanced comments on washing

    Last night (Saturday the 9th here), I was chatting in our chatroom while editing the fact sheet for the Super Universal Fix (tentative name for version VIII of the Super Fix). While doing it, someone asked me how many changes of water per unit time I used with running water and I answered, "I don't have a flow meter so I don't have an exact figure" which is a cop out!

    I have measured the flow rate of my water using graduates and 4 liter jugs, but this too is a copout. It does not explain the matter fully, so here I go.

    First, relating to one persons comments lets imagine a print lying on a tilted flat surface. Now, pour a liter of water over the print from the top down. The exchange rate is virtually infinite (dV/dT change in volume per unit time), but the volume itself is very low. Also, the bottom of the print sees contaminated water but the top of the print sees only fresh water. The wash is differential across the surface in spite of having a viturally infinite flow or exchange!

    Now, consider 3 reels of 120 film in a SS developing tank. As water flows in at the bottom (assuming a delivery system such as Jobo uses to put fresh water in from bottom to top), then the dV/dT is relatively huge per unit area of film but again there is a diminishing but real difference in the quality of the water from bottom to top.

    Enough water must be used in total so that the top reel of film is fully washed.

    If you use static changes of water, do you measure the wash time as a total value or do you start and stop the clock as you dump and refill. It can take 30 seconds to refill a tank. This changes the way you have to look at wash time compared to the last two paragraphs.

    Lets assume you use standing water and agitate by lift and dunk. On average, the bottom roll of film sees more fresh water during refill and more overall water during lift and dunk than the top roll. You have a differential introduced again across your film. The judge of extent of washing is again the top roll.

    Well, this just illustrates the fact that washing is hard to define. It is a function of flow rate, container shape and size, and agitation methods for film and for paper alike.

    Therefore, I don't judge wash as a measure of flow rate, exchanges or any other factor but rather - is it done at the end of 1 minute, 2 minutes, 3 minutes etc with my particular wash method whatever it may be. So, with a 5x7 tray, my flow rate would be slower than for an 8x10 tray, but for 1 print in an 8x10 tray it would be different than for 10 prints as would my agitation. This, just like photography itself becomes a lab technique (or an art) gained with experience, but only mastered by testing. If you don't test, you will not know where you are or were, ever.

    The one sure thing I can say is that as you use ever shorter wash times, the number of changes of water per unit time has to increase. For example, Kodak recommended 12 changes of water per hour for a 30 minute wash or 6 full changes of water. With a 5 minute wash at that rate, there is no time for even one change of water regardless of method used, and therefore the change rate has to go up. This cycle of increasing changes as time shortens eventually is self defeating. But, with a 5 minute wash, 3 changes would seem to be the minimum to me. With the static water method, this 5 minutes would have to exclude the refill time of the tank or tray after each dump.

    If wash rate dropped below 1 minute by some miracle of chemistry, then the flow rate would have to be huge, and there would be little gain in water usage.

    So, these are facts to consider. Use the most efficient method of water flow and the most efficient way of timing and agitation. Test your results and if the results satisfy you then adhere to them all of the time with no exception.

    Enclosed is a scan of a Kodak Hypo Test chart. Even though it is B&W, I am sure that you can visualize the densities as being pale yellow to darker brown from left to right.

    That is how I test my fixers, my film and my paper for quality of washing.

    PE
    Attached Thumbnails Attached Thumbnails Hypo test.jpg  

  3. #63

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    Quote Originally Posted by ozphoto View Post
    Water restrictions ... I want to reduce the amount of H2O
    I use as much as possible.
    How do you wash your prints and films to use the least
    amount of water possible?
    After the fixer is out of the tank 500ml of wash water is
    poured in and the first of Ilford's three wash sequence is
    under way. No quick 5 inversions; they are spaced out to
    allow for a more efficient use of the wash water. Same
    goes for the following 10 and 20 inversion 2nd and
    3rd washes. Actually I don't rush the washes at
    all. Some little clean up and putting away is
    also attended to while the film is washing.

    Total wash water, 1500ml. To that I add another 500ml
    for a PhotoFlo soak.

    I could reduce my wash water TOTAL to 500ml by use
    of the COUNTER CURRENT technique. By that technique
    only the last wash is fresh water. That last wash becomes
    the second to last with the next film to be washed. The
    second to last wash water becomes the third to last
    and so on. The first wash water is discarded. Likely
    I'd use four washes as all but the last wash have
    seen some use.

    Now if one is really, really serious about skimping
    on water, combine the counter current technique with
    ROTARY TANK washing. Rotary tanks use perhaps 1/2 the
    water. Likely a 5th wash a good idea. So, one could use as
    little as 1 cup or 250ml of water to wash one 120 roll. Dan

  4. #64

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    Some Reservations

    I've not tested the counter current or the rotary or the
    combination of both as methods of washing. So, I do not
    recommend any of the three. My previous post is more of
    a suggestion for use but any would need testing. If a LEAST
    amount of water for washing film is a goal then any of the
    three should be considered. Dan

  5. #65

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    Do devices like the Wat-Air film washer save any time, or do they just make it more sure-fire? Certainly is gets very good velocity on the water.

  6. #66
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    John, I cannot say as I never tested them. I have tested counter current and rotary wash as well as tank, basket and a variety of others. I have, in most cases, derived quantitative data in terms of mg/unit area of retained silver complexes and etc..

    Thats about all I can say.

    PE

  7. #67
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    Quote Originally Posted by Photo Engineer View Post
    Well guys, I'll post it again. BTW, I have re-read Mason and Jacobsen along with the Kodak technical manual. And Dan, your common sense is not correct here. Common sense told mankind that the earth was flat too, and the sun revolved around the earth!

    Here are the equations for washing:

    Diffusion rate governed washing dX/dT = k(a - X) where a = thiosulfate in the emulsion, X = loss in concentration over T which is time. This is read as the change in concentration per unit time.

    This is an exponetial when integrated as in:

    k = 1/T * Ln( a / a - x) where Ln = Log base 2

    So, if 80% washes out in 4 minutes, then 20% remains and 80% of that will take another 4 minutes. No matter what method is chosen, the residual silver complexes and hypo must have fallen to a level that gives the best image stability. Now, this equation only works at the instant of immersion when there is NO fixer or complexes in the wash water such as in freely running water with agitation.

    As washing proceeds in still water or agitated non running fresh water, the equation becomes:

    dX/dT = k[(a - x) - w] where w = the amount of salts built up in the wash water at any given time! The larger w becomes, the slower the wash becomes and in standing water (say any of the 5 or so changes you use) it becomes larger with time and is NEVER zero. In running water it can be made equal to zero.

    In addition, with FB paper, this equation does not apply at all due to the cellular nature of FB paper and the washing is very sluggish and can take up to several hours. So, this works only with film and RC paper.

    Mason goes on (as does Jacobsen) to describe the ideal wash being fresh water introduced into a final tank which overflows into the preceding tank and soforth for a series of tanks connected together. Jacobsen gives the diagram of this countercurrent wash which has been used for years by commercial photofinishers.

    Kodak simply says "wash the film in running water for 30 minutes..... at a rate sufficient to achieve about 12 turnovers / hour...". For FB paper it is 1 hour.

    Refernces: L. F. A. Mason of Ilford "Photographic Processing Chemistry"

    C. I. Jacobsen of Pavelle "Developing"

    Kodak B&W Darkroom Dataguide (2 suggestions - one for normal and one for archival use. I have quoted the archival above)

    PE
    Considering the study was done with in the 1970's when hardening hypo based fixers were common, and now we have the rapid (Ammonium Thiosulphate) non-hardening fixers, does the studies findings even apply to modern films, prints and chemistries?

  8. #68
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    Yes.

    Neutral and alkaline fixes were known in the 60s AAMOF. I sudied them extensively back then in a variety of equipment. And, I studied them across hardener types and with paper, across support types from FB to RC.

    PE

  9. #69

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    Just to go to the Oz's original question regarding environment - I let my wash water run into the garden. Nothing's died yet plant-wise, I have plenty frogs in the garden though...

  10. #70
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    Yes, except for the silver complexes, Ammonium Hypo and related compounds found in trace amounts in the wash are benign or good for plants. Ammonia is a plant fertilizer at near neutral pH and in low concentration such as is found in wash water.

    Blix and Ferric EDTA bleaches are good for Rhododendra, Azaleas and Oaks in dilute form.

    PE



 

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