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

[angusparker]

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?

[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

[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/2006130218312091.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-photo-film-processing-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

[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/display.cgi?item_num=90741

the webpage includes a link to the product data sheet.

[angusparker]

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

http://www.ctlscientific.com/cgi/display.cgi?item_num=90741

the webpage includes a link to the product data sheet.

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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[angusparker]

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/2006130218312091.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-photo-film-processing-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

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


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[angusparker]

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

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

- Leigh

See above.


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[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.

[angusparker]

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.

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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[Tin Can]

I ordered Ted's suggestion. http://www.ctlscientific.com/cgi/display.cgi?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...

[angusparker]

I ordered Ted's suggestion. http://www.ctlscientific.com/cgi/display.cgi?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...

Got a nasty shock when I tested mine - 5g/l which is 3 times the limited according to what is written above. Nothing really critical I've been doing lately on the film side which is good. Just playing around with my new old 11x14 so if the negatives fade etc I'm not too bothered.


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[Tin Can]

Got a nasty shock when I tested mine - 5g/l which is 3 times the limited according to what is written above. Nothing really critical I've been doing lately on the film side which is good. Just playing around with my new old 11x14 so if the negatives fade etc I'm not too bothered.


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I do a lot of X-Ray which is quickly given away to another person who wants negatives for other uses.

I keep a loose track of total sq ft and replace when suggested.

Everything I do will never be saved for eternity.

I'm trying to find the min/max with X-Ray.

[Tin Can]

Got a nasty shock when I tested mine - 5g/l which is 3 times the limited according to what is written above. Nothing really critical I've been doing lately on the film side which is good. Just playing around with my new old 11x14 so if the negatives fade etc I'm not too bothered.


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I tested 2 well used TF-5 batches with the strips.

Both TF-5 and never mixed together. Both 0.5 AG and PH 7.

[Doremus Scudder]

Keep in mind that there are different standards of acceptable dissolved silver in fixers for film and for paper. Film fixer can have a lot more silver in it and still do the job just fine. However, you don't need fancy test strips for film fixer; just do a clip test and keep track of clearing times. Toss the film fix when clearing time for a particular film is 2x that in fresh fix.

For fiber-base prints, the whole situation is more complicated. If you want archival permanence, use two-bath fixing and toss the first fix before its throughput capacity has been reached. This keeps the second bath fresh. You can also use a single-bath regime, just remember that the fixer capacity is kind of low (10 8x10s per liter or fewer). Test for residual silver/hypo too to check your process. Even these tests won't tell the whole story. It's best to "underuse" the fix and be sure.

Angus, I imagine that using the first print fix to 1.5g dissolved silver and then changing out would be a good starting point. You might be able to go a bit higher even, but, better to err on the side of underuse. I'd test the last print through the fixers for residual silver anyway, just for peace of mind.

Best,

Doremus

[angusparker]

Keep in mind that there are different standards of acceptable dissolved silver in fixers for film and for paper. Film fixer can have a lot more silver in it and still do the job just fine. However, you don't need fancy test strips for film fixer; just do a clip test and keep track of clearing times. Toss the film fix when clearing time for a particular film is 2x that in fresh fix.

For fiber-base prints, the whole situation is more complicated. If you want archival permanence, use two-bath fixing and toss the first fix before its throughput capacity has been reached. This keeps the second bath fresh. You can also use a single-bath regime, just remember that the fixer capacity is kind of low (10 8x10s per liter or fewer). Test for residual silver/hypo too to check your process. Even these tests won't tell the whole story. It's best to "underuse" the fix and be sure.

Angus, I imagine that using the first print fix to 1.5g dissolved silver and then changing out would be a good starting point. You might be able to go a bit higher even, but, better to err on the side of underuse. I'd test the last print through the fixers for residual silver anyway, just for peace of mind.

Best,

Doremus

I've made myself a fancy laminated sheet with checkboxes that after I have completed each set of boxes should mean the fix is spent. A sheet of 4x5 = 0.25 of a check, 120 = 1, 8x10 = 1, 11x14 =2 and 14x17 = 3 units and so on - following the manufacturers guidelines on film fixing. I'll back this up with the occasional check closer to the end to see what the dissolved Ag is.

[Doremus Scudder]

I've made myself a fancy laminated sheet with checkboxes that after I have completed each set of boxes should mean the fix is spent. A sheet of 4x5 = 0.25 of a check, 120 = 1, 8x10 = 1, 11x14 =2 and 14x17 = 3 units and so on - following the manufacturers guidelines on film fixing. I'll back this up with the occasional check closer to the end to see what the dissolved Ag is.

Angus,

At the risk of sounding like a broken record, let me stress again that the best way to test film fixer for exhaustion is with a clip test for clearing time. Sure, keeping track of throughput is a good idea but the clip test is more accurate as it tests the fix itself. Throughput assumes average density for all negatives; your fixer will exhaust faster more thin negs are run through it... Additionally, allowable dissolved silver content is much higher for film fixers than for print fixers. Consult the Ilford fact sheet I linked to earlier for more exact info. Do not use fixer used for film for prints. The by-products from fixing film will negatively affect the paper fixing process.

The advice I've given you above is mainly for fixing fiber-base prints. This is the critical step and where the dissolved silver must be kept very low for archival permanence.

Best,

Doremus

[Pere Casals]

Useful advice, I'll follow it.

[Tin Can]

Doremus,

Good to know I already follow best practice. I do use different batches of fix for film and paper. Even 2 different formulae to eliminate confusion.

I do a clip test before every usage of either fixer with strips of left over X-Ray film cuttings.

I also count footage as Angus does.

The ag/ph test strips aren't expensive and confirm my methods.

I still consider myself a novice and an old man with increasing brain fade, repetitive confirmation is necessary. For me.

[angusparker]

Angus,

At the risk of sounding like a broken record, let me stress again that the best way to test film fixer for exhaustion is with a clip test for clearing time. Sure, keeping track of throughput is a good idea but the clip test is more accurate as it tests the fix itself. Throughput assumes average density for all negatives; your fixer will exhaust faster more thin negs are run through it... Additionally, allowable dissolved silver content is much higher for film fixers than for print fixers. Consult the Ilford fact sheet I linked to earlier for more exact info. Do not use fixer used for film for prints. The by-products from fixing film will negatively affect the paper fixing process.

The advice I've given you above is mainly for fixing fiber-base prints. This is the critical step and where the dissolved silver must be kept very low for archival permanence.

Best,

Doremus

Great advice. I have separate fix for film and paper. I'll end up doing both I think - check throughput to let me know when I'm in the ballpark and then the clip test / test strip.

[Doremus Scudder]

Great advice. I have separate fix for film and paper. I'll end up doing both I think - check throughput to let me know when I'm in the ballpark and then the clip test / test strip.

I notice that I'm still not as clear as I'd like to be. Just so there's no confusion and to summarize our results:

Separate fixers for film and prints.

Clip-test for film fix to determine exhaustion. When the clearing time reaches 2x that in fresh fix, discard the fixer.

Keeping track of throughput and two-bath fixing for fiber base prints. If you use the test strips, test the first bath and discard when dissolved silver reaches 1.5-2g/liter. Add to this tests for residual silver and hypo to confirm your workflow.

Best,

Doremus