At what level of Ag g/L should I replace fix?

I've got some great test strips that give me the silver content and PH of my fix. I was wondering what the highest acceptable level of silver content is in fix before you can say it is exhausted?

Could you identify the maker and catalog number of those strips?

I'm sure it would be of interest to the assembled eyeballs.

- Leigh

It depends...

There are a more than one standard for fixation. The amount of allowable dissolved silver in a fix depends on the degree of print permanence you desire. Ilford, their fact sheet on their Rapid Fixer, allow 2g/liter of dissolved in the last fixing bath for "a high level of image permanence is required for commercial use." And further, "For prints that need maximum stability for long term storage a the maximum silver level in the fixer should not rise above 0.5 g/liter." Check out the Ilford fact sheet here: http://www.ilfordphoto.com/Webfiles/...0218312091.pdf

As you can see, Ilford has two standards, "commercial use" and what we could call "optimum permanence," or "archival." To make things more complicated, Grant Haist, former head of research at Kodak recommends even less dissolved silver for these same two standards, i.e., 1.5 g/liter and 0.2 g/liter respectively (quoted by Gudzinowicz here: http://photo.net/black-and-white-pho...g-forum/007dXZ ). He gives 0.05 g/liter for the second bath of a two-bath fixing regime for "archival" permanence. Haist, however, is speaking about conventional sodium thiosulfate based fixers. The capacity of ammonium thiosulfate rapid fixers should be higher (hence, likely, the larger capacity Ilford gives for it's Rapid Fixer).

I'm not sure if the test strips you have are sensitive enough to accurately read 0.5 g/liter of dissolved silver in a fixing bath, much less Haist's 0.05 g/liter. If so, then choose your standard and you're in business. If not, you may want to look into testing for residual silver and hypo and develop a workflow that consistently gives you the results you want. Use Kodak ST-1 or Kodak Rapid Selenium Toner 1+9 as a reagent for testing for residual silver (fixing). The Kodak HT-2 test works for residual hypo (washing). There's a lot here and on APUG about how to mix and use both test solutions, etc., etc. if you're interested.

Do let us know what test strips you have and what their sensitivity is. If sufficiently sensitive, I would be interested in some.

Best,

Doremus

There is a European product made by Machery-Nagel, also available in the USA, I purchased some recently

http://www.ctlscientific.com/cgi/dis...item_num=90741

the webpage includes a link to the product data sheet.

Quote:

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Originally Posted by Ted R

There is a European product made by Machery-Nagel, also available in the USA, I purchased some recently

http://www.ctlscientific.com/cgi/dis...item_num=90741

the webpage includes a link to the product data sheet.

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These are the ones I have. Maximum sensitivity is 0.5 g/l which if I go for 1.5g/l as my standard should work but perhaps I should just count 8x10 film equivalents and do it the calculation way.


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Quote:

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Originally Posted by Doremus Scudder

It depends...

There are a more than one standard for fixation. The amount of allowable dissolved silver in a fix depends on the degree of print permanence you desire. Ilford, their fact sheet on their Rapid Fixer, allow 2g/liter of dissolved in the last fixing bath for "a high level of image permanence is required for commercial use." And further, "For prints that need maximum stability for long term storage a the maximum silver level in the fixer should not rise above 0.5 g/liter." Check out the Ilford fact sheet here: http://www.ilfordphoto.com/Webfiles/...0218312091.pdf

As you can see, Ilford has two standards, "commercial use" and what we could call "optimum permanence," or "archival." To make things more complicated, Grant Haist, former head of research at Kodak recommends even less dissolved silver for these same two standards, i.e., 1.5 g/liter and 0.2 g/liter respectively (quoted by Gudzinowicz here: http://photo.net/black-and-white-pho...g-forum/007dXZ ). He gives 0.05 g/liter for the second bath of a two-bath fixing regime for "archival" permanence. Haist, however, is speaking about conventional sodium thiosulfate based fixers. The capacity of ammonium thiosulfate rapid fixers should be higher (hence, likely, the larger capacity Ilford gives for it's Rapid Fixer).

I'm not sure if the test strips you have are sensitive enough to accurately read 0.5 g/liter of dissolved silver in a fixing bath, much less Haist's 0.05 g/liter. If so, then choose your standard and you're in business. If not, you may want to look into testing for residual silver and hypo and develop a workflow that consistently gives you the results you want. Use Kodak ST-1 or Kodak Rapid Selenium Toner 1+9 as a reagent for testing for residual silver (fixing). The Kodak HT-2 test works for residual hypo (washing). There's a lot here and on APUG about how to mix and use both test solutions, etc., etc. if you're interested.

Do let us know what test strips you have and what their sensitivity is. If sufficiently sensitive, I would be interested in some.

Best,

Doremus

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Very helpful 1.5g/l seems a safe level. Thoughts?


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Quote:

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Originally Posted by Leigh

Could you identify the maker and catalog number of those strips?

I'm sure it would be of interest to the assembled eyeballs.

- Leigh

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See above.


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I'm lazy. I use TF4 fixer one-shot, mixing enough for the handful of prints I tend to complete in a one-day session, and then out it goes. I've very confident about
the archival aspect.

Quote:

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Originally Posted by Drew Wiley

I'm lazy. I use TF4 fixer one-shot, mixing enough for the handful of prints I tend to complete in a one-day session, and then out it goes. I've very confident about
the archival aspect.

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I do the same for prints but recycle for film. But then I sometimes do 10 8x10 or several 11x14 at a time which is a lot of surface area....


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I ordered Ted's suggestion. http://www.ctlscientific.com/cgi/dis...item_num=90741

I use and reuse TF-5 for film only and have not found it's exhaustion. It always clears quickly, I go by time. I store it in 5-gallon tanks pouring the used back in. I guess I better find out where it fails the Kodak parameter.

Testing with Edwal Hypo Check reveals nothing, no exhaustion...