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#1
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Fix bath test
I've found two formulation to prepare fix bath test solution:
- using 50 g / l of potassium iodide or - using 190 g / l of the same salt What is the best? Thanks ziocalepino |
#2
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Fix bath test
And I use10% (= 100 g / l). Am I doing something stupid...?
Jan "piterengel" schreef in bericht m... I've found two formulation to prepare fix bath test solution: - using 50 g / l of potassium iodide or - using 190 g / l of the same salt What is the best? Thanks ziocalepino |
#3
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Fix bath test
RE
I've found two formulation to prepare fix bath test solution: - using 50 g / l of potassium iodide or - using 190 g / l of the same salt What is the best? Both will work though approximately four times as much of the 50gr/ltr solution will be needed. If counting drops is no bother, the more drop method will give you a more accurate quantitative result. A weakness of the usuall test method is that it does not really give a good indication of how close is the fix to exhaustion. A fix may pass the usuall test then after the next roll of film or two or three prints, it may fail. The many drop method may help pin down just how much life is left. Dan |
#4
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Fix bath test
Dan,
can you describe that method, please? Jan "Dan Quinn" schreef in bericht m... RE I've found two formulation to prepare fix bath test solution: - using 50 g / l of potassium iodide or - using 190 g / l of the same salt What is the best? Both will work though approximately four times as much of the 50gr/ltr solution will be needed. If counting drops is no bother, the more drop method will give you a more accurate quantitative result. A weakness of the usuall test method is that it does not really give a good indication of how close is the fix to exhaustion. A fix may pass the usuall test then after the next roll of film or two or three prints, it may fail. The many drop method may help pin down just how much life is left. Dan |
#5
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Fix bath test
"Jan T" wrote
And I use10% (= 100 g / l). Am I doing something stupid...? WE may be doing something stupid. I think perhaps that the iodide test is another of those one ... fits-all recommendations. The usuall thiosulfate fix, sodium or ammonium, can take up small amounts of silver in the presence of small amounts of iodide. But the same fix can take up large amounts of silver in the presence of it's chloride and bromide. In fact in the presence of chloride and to a lesser extent bromide, silver may be complexed by the ammonia. The iodide test is important in my work because I use fixer one- shot and do not wish to waste it. I conducted a fix test some time ago with iodide and then tested with bromide. Where the iodide produced a precipitate with a few drops the bromide did not with several times as much of it added. I will be doing more titration tests with iodide and bromide. BUT, there is a relation ship twixt the iodide and bromide tests. If the ratios are correct then the iodide test is valid. I'll have to do some more tests to come to an accurate quantitative determination. I think though you can see my point. If in the fix test I made, a very few drops of iodide made for, but a nearly endless number of bromide made not for a precipitate, then how close to accurate can the test be? Dan |
#6
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Fix bath test
"piterengel" wrote in message m... I've found two formulation to prepare fix bath test solution: - using 50 g / l of potassium iodide or - using 190 g / l of the same salt What is the best? Thanks ziocalepino Here is Kodak's formula: Kodak FT-1 Fixer Bath Test Solution Water at 80F (27C) 750.0 ml Potassium Iodide 190.0 grams Water to make 1.0 liter To test a single bath fixer: To 5 drops of the test solution, add 5 drops of the fixing bath and 5 drops of water. Discard the fixer if a yellow-white precipitate forms instantly. Disregard any slight milkiness. Two Bath Fixer: First Bath: Test as described above for a single bath. Second Bath: To 5 drops of test solution add 5 drops of fixing solution plus 15 drops of water. If _both_ tests produce a yellow-white precipitate, replace both baths with fresh baths. If only the first bath forms a precipitate, replace the forst bath withyt the second bath, and replace the second bath with a fresh bath. The test solution can be stored for one year in a stoppered brown bottle. A liter of this stuff is a lifetime supply. The formulas are standardized to 1.0 liter. I think 50 ml is a more practical amount. This test works on either sodium or ammonium (rapid) fixers although the criteria above are probably for sodium thiosulfate and prints. The formula you have using 50 grams per liter is about the same as the diluted version of this test for single bath fixers. -- --- Richard Knoppow Los Angeles, CA, USA |
#7
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Fix bath test
"Richard Knoppow" wrote
Here is Kodak's formula: Kodak FT-1 Fixer Bath Test Solution Water at 80F (27C) 750.0 ml Potassium Iodide 190.0 grams Water to make 1.0 liter To test a single bath fixer: To 5 drops of the test solution, add 5 drops of the fixing bath and 5 drops of water. Discard the fixer if a yellow-white precipitate forms instantly. Disregard any slight milkiness. Those directions are telling us to add 5 drops fixing bath to 5 drops of 19% KI solution. That is an unrealistic test save for possably one. That one would be a single bath archival fix. Silver levels as you know must be very low in a first and only fix to achieve archival results. I'm quite sure bath one and two fixers have been reversed. That is, 15 drops of water should be added to test bath one and 5 drops added to bath two. That will dilute bath two less and make for a more sensitive test. Bath two silver levels are to be kept extremly low. One more thing, this FT-1 test is for, if anything, Fiber Base paper ONLY. Quite frankly I'm not sure the FT-1 test is good for anything but selling more fixer. Subclub recommends two, 2, DROPS same strength in 2 OUNCES of fix. My bottle of Fix-A-Sure recommends one, 1, DROP in 1 OUNCE. Those two are mentioned only by way of contrast. Dan Two Bath Fixer: First Bath: Test as described above for a single bath. Second Bath: To 5 drops of test solution add 5 drops of fixing solution plus 15 drops of water. If _both_ tests produce a yellow-white precipitate, replace both baths with fresh baths. If only the first bath forms a precipitate, replace the forst bath withyt the second bath, and replace the second bath with a fresh bath. The test solution can be stored for one year in a stoppered brown bottle. A liter of this stuff is a lifetime supply. The formulas are standardized to 1.0 liter. I think 50 ml is a more practical amount. This test works on either sodium or ammonium (rapid) fixers although the criteria above are probably for sodium thiosulfate and prints. The formula you have using 50 grams per liter is about the same as the diluted version of this test for single bath fixers. |
#9
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Fix bath test
"Jan T" wrote
Dan, can you describe that method, please? Jan RE I've found two formulation to prepare fix bath test solution: - using 50 g / l of potassium iodide or - using 190 g / l of the same salt What is the best? Both will work though approximately four times as much of the 50gr/ltr solution will be needed. If counting drops is no bother, the more drop method will give you a more accurate quantitative result. A weakness of the usuall test method is that it does not really give a good indication of how close is the fix to exhaustion. A fix may pass the usuall test then after the next roll of film or two or three prints, it may fail. The many drop method may help pin down just how much life is left. Dan The Kodak FT-1 and Subclub, Fix-A-Sure tests referred to in another post this thread, represent the extrems. The Kodak test and the other one-drop-in an-ounce tests are at opposite ends of the spectrum. One drop in one ounce is no margine at all. I see I've 5% KI. The 10% you use should show no precipitate with a few drops in 10ml. That is my opinion. I think I would feel safe with that. Do the test slowly, one drop at a time, and stir or shake. I've yet to read anything at all which delves into the subject of fixer testing. Considering the importance of fixation, I think the lack of information a real oversight. Some films and most papers have no silver iodides. Fixer has a great capacity for the chloride and bromide. Is the iodide test relevant? If so how is it related? The test itself, is it for film, RC or FB paper? In all cases capacity is not the measure. In fact the capacity of all usuall fixers surpass their usefullness; the more true with FB archivaly processed. Dan |
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