Objective measure of rapid fixer exhaustion (printing)?

I use Ryuji Suzuki's Neutral Fix for two-bath print fixing and track the number of prints I put through each batch. My current Bath 1 (about 2 liters/quarts, both baths mixed fresh a few weeks ago) has 57 11x14 prints through it. There's no precipitate with Edwal Hypo-Check (what's in that stuff??) and the testing papers I got recently say there's about 1/4 troy ounce per gallon. Is there a generally-accepted silver concentration at which a rapid fix for printing is considered exhausted? I know two-bath has a higher capacity than a single bath, but with paper a "clip test" is a lot less obvious than with film.

This is really just a curiosity question and I have no intentions of trying to go right up to the very edge - I plan to promote Bath 2 today and mix a new Bath 2. But the engineer in me needs to know this stuff, just because.

Use a film strip?

Steve Goldstein said:

I use Ryuji Suzuki's Neutral Fix for two-bath print fixing and track the number of prints I put through each batch. My current Bath 1 (about 2 liters/quarts, both baths mixed fresh a few weeks ago) has 57 11x14 prints through it. There's no precipitate with Edwal Hypo-Check (what's in that stuff??) and the testing papers I got recently say there's about 1/4 troy ounce per gallon. Is there a generally-accepted silver concentration at which a rapid fix for printing is considered exhausted? I know two-bath has a higher capacity than a single bath, but with paper a "clip test" is a lot less obvious than with film.

This is really just a curiosity question and I have no intentions of trying to go right up to the very edge - I plan to promote Bath 2 today and mix a new Bath 2. But the engineer in me needs to know this stuff, just because.

Click to expand...

57 x 11" x 14" exceeds the general recommendations for 'commercial' standard (2 g/l Silver) prints and far exceeds the accepted archival standards (0.5 g/l Silver). Many photographic scientists and Ilford themselves state that testing papers are only suitable for testing fixer to ensure 'commercial' standard prints.

So the first question is to what standards to you wish to process your prints?

The ‘rule of thumb’ for the maximum silver concentration in fibre-based papers when you wish to achieve archival standards is to ensure that the silver in the fixer remains below 0.5 g/l. This is roughly equivalent to 20 x 8” x 10” prints FB prints in 2L of rapid fixer mixed at 1 + 4 (but of course is somewhat dependent upon how much of the paper’s silver was used to form the image / how much unused silver the fixer has to remove.

What I personally do with my 2L fix bath A is ensure that no more than 10 sheets of 16” x 12” paper (plus test strips) passes through the bath A before it is discarded.

My 2L fix bath B is also limited to 10 sheets of 16” x 12” paper before it is transferred to be fix bath A.

These figures are based upon a test that I do every year in January. This test is the one published by Ilford some time ago:

Prepare the testing solution by dissolving 2g of sodium sulphide in 125ml of water. NB Take care to follow the health and safety information supplied by sodium sulphide manufacturer.

For use, dilute the testing solution 1+9 with water.

To establish a permanent reference for a particular type of paper, place a drop of the diluted testing solution on a white area of a print that is known to be well fixed and thoroughly washed. (Use the two bath fixing method). Remove any excess solution with clean blotting paper or absorbent tissue and a barely visible cream tint should be left. This is the reference colour for a well fixed and washed print on this type of paper.

Any subsequent prints that show a yellowing of the test spot when tested are not properly fixed.

Prints must be well washed before using the test, it is not effective on prints direct from the fixer bath.

Click to expand...

Bests,

David.
www.dsallen.de

Use a film strip?

Click to expand...

+1
That's what I do all the time. Whether fimm fixer or paper fixer. But need a reference clearing time with fresh fixer; FWIW, my reference times with any rapid-type fixers are:
- 1+4 dilution : 20-25s
- 1+9 dilution : 60s
Discard when clearing time has doubled. Fix for at least twice the current clearing time.
If you miss a reference time, just prepare a small quantity of fresh fixer to establish that; when done pour into old fixer: can't hurt.

David Allen said:

57 x 11" x 14" exceeds the general recommendations for 'commercial' standard (2 g/l Silver) prints and far exceeds the accepted archival standards (0.5 g/l Silver). Many photographic scientists and Ilford themselves state that testing papers are only suitable for testing fixer to ensure 'commercial' standard prints.

So the first question is to what standards to you wish to process your prints?

The ‘rule of thumb’ for the maximum silver concentration in fibre-based papers when you wish to achieve archival standards is to ensure that the silver in the fixer remains below 0.5 g/l. This is roughly equivalent to 20 x 8” x 10” prints FB prints in 2L of rapid fixer mixed at 1 + 4 (but of course is somewhat dependent upon how much of the paper’s silver was used to form the image / how much unused silver the fixer has to remove.

What I personally do with my 2L fix bath A is ensure that no more than 10 sheets of 16” x 12” paper (plus test strips) passes through the bath A before it is discarded.

My 2L fix bath B is also limited to 10 sheets of 16” x 12” paper before it is transferred to be fix bath A.

These figures are based upon a test that I do every year in January. This test is the one published by Ilford some time ago:


Bests,

David.
www.dsallen.de

Click to expand...

I agree fully with David

The Edwal test solution is a solution of potassium iodide in water. Silver iodide is the least soluble of the silver halides. So its formation is a sign that the fixer is reaching exhaustion. However the test is not that accurate as usually performed. The best method is to compare the number of prints with the recommended maximum number of prints.

Whether you are testing film or paper fixer your clip test must be done with a bit of film.

David Allen said:

57 x 11" x 14" exceeds the general recommendations for 'commercial' standard (2 g/l Silver) prints and far exceeds the accepted archival standards (0.5 g/l Silver). Many photographic scientists and Ilford themselves state that testing papers are only suitable for testing fixer to ensure 'commercial' standard prints.

So the first question is to what standards to you wish to process your prints?

The ‘rule of thumb’ for the maximum silver concentration in fibre-based papers when you wish to achieve archival standards is to ensure that the silver in the fixer remains below 0.5 g/l. This is roughly equivalent to 20 x 8” x 10” prints FB prints in 2L of rapid fixer mixed at 1 + 4 (but of course is somewhat dependent upon how much of the paper’s silver was used to form the image / how much unused silver the fixer has to remove.

What I personally do with my 2L fix bath A is ensure that no more than 10 sheets of 16” x 12” paper (plus test strips) passes through the bath A before it is discarded.

My 2L fix bath B is also limited to 10 sheets of 16” x 12” paper before it is transferred to be fix bath A.

These figures are based upon a test that I do every year in January. This test is the one published by Ilford some time ago:


Bests,

David.
www.dsallen.de

Click to expand...

I'm a little amazed by these numbers. If I remember correctly, Ilford says that it's possible to fix up to 100 8x10 sheets in one liter of working strength fixer (1:4).

This is 10X more then your calculation of 10 8x10 sheets in 1 liter of fixer (20 sheets in 2 liters).

NB23 said:

I'm a little amazed by these numbers. If I remember correctly, Ilford says that it's possible to fix up to 100 8x10 sheets in one liter of working strength fixer (1:4).

This is 10X more then your calculation of 10 8x10 sheets in 1 liter of fixer (20 sheets in 2 liters).

Click to expand...

Ilford's data sheet for their Rapid Fixer lists a capacity of 40 8x10 FB sheets per litre of working strength fixer.

David's approach yields 10 8x10 FB sheets per litre of working strength fixer, or 1/4 as much.

NB23 said:

I'm a little amazed by these numbers. If I remember correctly, Ilford says that it's possible to fix up to 100 8x10 sheets in one liter of working strength fixer (1:4).

This is 10X more then your calculation of 10 8x10 sheets in 1 liter of fixer (20 sheets in 2 liters).

Click to expand...

MattKing said:

Ilford's data sheet for their Rapid Fixer lists a capacity of 40 8x10 FB sheets per litre of working strength fixer.

David's approach yields 10 8x10 FB sheets per litre of working strength fixer, or 1/4 as much.

Click to expand...

Here we go again!

Here's the link to the Ilford data sheet for their Rapid Fixer, which we need to read again and more carefully and between-the-lines: http://www.ilfordphoto.com/Webfiles/2006130218312091.pdf

Yes, on page 2 Ilford gives a capacity of 40 8x10 sheets per liter for fiber-base paper and both dilutions of its Rapid Fixer (unreplenished) and even mentions that "The figures for paper may be exceeded whenever print stability is not critically important."

However, Ilford is here assuming a "commercial" or "general-purpose" standard for fixing. We must continue reading... Skip to page 4 under the section entitled, "Silver Concentration." There we find the fine print. For those too lazy to follow the link, I'll quote (with my emphasis):

"The level of silver that can be tolerated in a paper fixing bath depends on the type of paper being processed and the degree of image permanence required.

If a high level of image permanence is required for commercial use the silver concentration in the fixer should be kept below 2 g/l when fixing FB papers. This approximates to 40, 20.3 x 25.4 cm, (8 x 10 inch) FB prints. Above this level compounds may remain in the paper base after washing and over time possibly contribute to print staining.

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/l i.e. approximately 10 20.3 x 25.4cm (8 x 10in) prints."

Note that the above is for single-bath fixation, which Ilford recommends (remember their "archival sequence"?). Most exhibiting art photographers wish to work to "archival" standards and process for "optimum permanence," and therefore, according to the above, should only be processing 10 8x10 prints per liter of working-solution fixer with the one-bath method; NOT the 40 8x10s per liter that corresponds to "commercial" standards.

The trick, however, and what is not clear from the Ilford sheet, is how a two-bath fixing regime will affect capacity. The idea of two-bath fixing is to ensure that the bulk of the fixing is done in bath one and that bath two remains relatively fresh and contains less than the 0.5g/l of dissolved silver which is the limit for fixing to optimum permanence. The dissolved silver in fixing in bath one, however, can safely rise to the "commercial" level before being discarded as long as the second bath remains below the limit.

So (and now I'm going to contradict David Allen, which I don't really like doing, but...), 40 8x10s through bath one raises its level of dissolved silver to the limit for "commercial" work. Most of the fixing is done in this bath; in fact, Ilford (and Kodak, etc.) accept this amount of fixing as adequate for general-purpose work. But we want more: we want "archival." So we transfer the prints to a second, fresh bath of fixer. There is now only a tiny bit of fixing remaining to be done, so bath two doesn't do much work, in fact, after 40 prints (that have already been through bath one), its dissolved silver level should be at or below the 0.5g/l threshold for optimum permanence. At this point in the throughput, the first bath should be discarded and the second bath moved into its place. A fresh second bath is then mixed. This regime of replacing the first bath with second bath can go through seven iterations (this according to Kodak) before both baths should be mixed fresh and the whole thing started over.

Conclusion: two-bath fixing should have a capacity of 40 8x10s per... WAIT! per what?? Per one liter divided into two baths of 500ml each? Or two liters divided into two baths of one liter each? If we've been following the logic here, it should be apparent that we need the latter, i.e., two baths of one liter each (for two liters total). Yes, we get to re-use half of that when we promote the second fix to the first; that's where the economy and efficiency of two-bath fixing comes in.

And, we should also be aware that the above is a generalization, based on the "average" amount of silver converted to image silver in prints. If I'm printing a ton of snow scenes with hardly any image silver, that's going to result in more silver compounds needing to be fixed out and a corresponding drop in fixer capacity when measured in throughput. As Ilford says, "... print throughput can only be a guide to silver concentration as it depends on the proportion of exposed to unexposed areas on the prints being processed." They go on to recommend testing: "For important prints it is recommended that paper is tested ... to ensure adequate fixing" and go on to describe the test for residual silver (basically the Kodak ST-1 test).

Summary: Decide what standard you want to work to. If, like me, you want optimum permanence, then use throughput guidelines similar to what Ilford recommends for "maximum stability" and two-bath fixing. For me, that's 36 8x10s per liter each of two fixes (a bit of a safety factor plus the fact that multiples of 12 fit my washers). But don't stop there; test your prints and washing regime regularly and often. I test the last print through the second fix every time for both residual silver (ST-1) and residual hypo (HT-2). Often I'll send a blank sheet through as the last sheet so I can test a full sheet or at least several areas center and edge with drop tests. FWIW, I've never had a problem with prints passing both these tests using this fixing regime plus a wash-aid and a thorough 60-minute wash with a complete dump and refill of the washer halfway through the wash cycle.

Best,

Doremus

As Doremus explained in detail, if you read the Ilford instruction sheet carefully, you will see that they actually give three recommendations for the level of silver concentration in the fixer and this depends upon type of paper and final use:

• 8g/L (equals 160 prints size 10” x 8”) - This is for RC papers being used by hobby photographers.
• 2g/L (equals 40 prints size 10” x 8”) - This is for fibre-based papers needing to meet commercial standards
• 0.5g/L (equals 160 prints size 10” x 8”) - This is for fibre-based papers needing to meet archival standards

Also, I do not have any problem with the throughput that Doremus mentioned. The key point is not what I or Doremus do but that you need to do a test to ensure that you are fixing to the level of permanence that you require - should this be important to you.

My personal sequence that I mentioned is just what suits my workflow and was provided simply as an example. Perhaps I should have explained the following that my limit of 10 prints in each fixer bath is based upon:

• Annual tests to establish fixer capacity for a high key print (which I rarely make for myself but do make for some clients and it must be remembered that these are the most demanding types of print for a fixer bath to handle due to the high levels of silver released into the fixer bath).
• Ten 16” x 12” prints are roughly the equivalent of twenty 10” x 8” prints.
• My archival washer can accommodate ten prints size 16” x 12”.
• I use Adox Rapid Fixer and this, here in Berlin, costs 22.61€ for 5 Litres. Using two 2 L fixer baths mixed at 1 + 4 requires 1 L of fixer concentrate. This works out at approximately 42 cents per final print. Given that I wanted to build in a high level safety factor into my processing sequence, that I spend many hours searching for the subjects that I photograph, hours carefully processing and printing my negatives I do not find (especially when considering price of paper, time invested, etc) spending 42 cents per final print to be high a price to pay.

Anyway, the core message is one should test (annually is enough) to check that you are achieving the level of permanence that suits your work.

Bests,

David.
www.dsallen.de

I tone all my finished prints, with selenium, sepia or both. I figure most serious printers do the same. If your prints are under fixed, or your process is poor leading up to that point, it becomes very apparent in the form of staining.

So toning is a twofold benefit: One, it makes your prints look better. Two it verifies your process is correct. This is no small thing; it removes that shadow of doubt that many printers feel.

Ilford makes note of this in their Toning B&W Prints pdf. They use the phrase "instant test of adequate fixing", which I think is a good way of putting it.

Marco Buonocore said:

I tone all my finished prints, with selenium, sepia or both. I figure most serious printers do the same. If your prints are under fixed, or your process is poor leading up to that point, it becomes very apparent in the form of staining.

So toning is a twofold benefit: One, it makes your prints look better. Two it verifies your process is correct. This is no small thing; it removes that shadow of doubt that many printers feel.

Ilford makes note of this in their Toning B&W Prints pdf. They use the phrase "instant test of adequate fixing", which I think is a good way of putting it.

Click to expand...

I'm not sure.

Inadequate washing leads to bad toning.

A bad rinse after the fixing will cause stains in the toner.
A not thorough fixed image will not necessarily show stains after having been selenium toned.

Selenium toning is a last step of many steps towards archival status of a print. As in a chain, all steps must comply to archival standards in order for the print to be archival.

David Allen said:

As Doremus explained in detail, if you read the Ilford instruction sheet carefully, you will see that they actually give three recommendations for the level of silver concentration in the fixer and this depends upon type of paper and final use:

• 8g/L (equals 160 prints size 10” x 8”) - This is for RC papers being used by hobby photographers.
• 2g/L (equals 40 prints size 10” x 8”) - This is for fibre-based papers needing to meet commercial standards
• 0.5g/L (equals 160 prints size 10” x 8”) - This is for fibre-based papers needing to meet archival standards

Also, I do not have any problem with the throughput that Doremus mentioned. The key point is not what I or Doremus do but that you need to do a test to ensure that you are fixing to the level of permanence that you require - should this be important to you.

My personal sequence that I mentioned is just what suits my workflow and was provided simply as an example. Perhaps I should have explained the following that my limit of 10 prints in each fixer bath is based upon:

• Annual tests to establish fixer capacity for a high key print (which I rarely make for myself but do make for some clients and it must be remembered that these are the most demanding types of print for a fixer bath to handle due to the high levels of silver released into the fixer bath).
• Ten 16” x 12” prints are roughly the equivalent of twenty 10” x 8” prints.
• My archival washer can accommodate ten prints size 16” x 12”.
• I use Adox Rapid Fixer and this, here in Berlin, costs 22.61€ for 5 Litres. Using two 2 L fixer baths mixed at 1 + 4 requires 1 L of fixer concentrate. This works out at approximately 42 cents per final print. Given that I wanted to build in a high level safety factor into my processing sequence, that I spend many hours searching for the subjects that I photograph, hours carefully processing and printing my negatives I do not find (especially when considering price of paper, time invested, etc) spending 42 cents per final print to be high a price to pay.

Anyway, the core message is one should test (annually is enough) to check that you are achieving the level of permanence that suits your work.

Bests,

David.
www.dsallen.de

Click to expand...

I see. I print my 20x24 and 16x20 within the 1.0-0.5 range. However, I was really sure that even 2.0 was well within the archival range. Now I stand corrected.

Marco Buonocore said:

I tone all my finished prints, with selenium, sepia or both. I figure most serious printers do the same. If your prints are under fixed, or your process is poor leading up to that point, it becomes very apparent in the form of staining.

So toning is a twofold benefit: One, it makes your prints look better. Two it verifies your process is correct. This is no small thing; it removes that shadow of doubt that many printers feel.

Ilford makes note of this in their Toning B&W Prints pdf. They use the phrase "instant test of adequate fixing", which I think is a good way of putting it.

Click to expand...

hi Marco

I've been printing since 1981' and printing commercially since 1986 and I never tone anything.
not sure if it has to do with seriousness or preference. personally, I want nothing to do
with selenium or other nasty chemicals. i worked for someone who for IDK 60 years or more had
a portrait studio .. she exposed cases of 5x7 film and sold prints by the armload daily ..
she never toned anything either. we DID keep track of how many prints were put through the 5 gallon tank of film fixer
as well as the 6 inch deep tub of print fixer ... we trusted the manufacturer ( kodak at the time )'s capacity numbers
and never really used hypo check ( most people use hypo check wrong anyways )
since then i started doing the clip test ( use double baths ) and when it is 2x the original clear time i use the magnet to extract silver from the saturated fixer,
or a trickle tank for wash water or fixer i am "nervous" about .. there are a few different fixer capacity tests that give an idea of amounts of silver in one's fixer
if they are nervous about clip tests or how accurate the capacities might be ... either way double fixer baths seem to work well.

i've known people who toned prints ( with selenium or or sepia ) and they didn't really care about toxicity issues like me
and they were pretty serious ...

NB23 said:

...
A not thorough fixed image will not necessarily show stains after having been selenium toned...

Click to expand...

It will. It is a method proposed by Kodak for this purpose. The dilution they mention is 1+9, although they state that it isn't critical. Compared to an untoned print, there might be a slight, but even stain, which might be more difficult to spot, but its there.

Anon Ymous said:

It will. It is a method proposed by Kodak for this purpose. The dilution they mention is 1+9, although they state that it isn't critical. Compared to an untoned print, there might be a slight, but even stain, which might be more difficult to spot, but its there.

Click to expand...

I agree that a stain will appear, but not instantly. Over time, a print will start talking about how archival it really is. But that takes time and exposure to air. That's my own theory based on the actual theory.

I have never had this staining happen to me, even when I was sure I underfixed a print and then selenium toned it. However, I've had well fixed prints show stains and that was clearly because the print was not well rinsed and still had a good amount of fixer on it which reacted with the selenium.

I have people who say their prints are bad after 3 years but all of mine I still have are good after sixty etc. Depending on when they were printed.

Fresh fix and lots of time in sink syphon...

Little point in using expensive paper and developer and risking fixing or washing.

Anon Ymous said:

It will. It is a method proposed by Kodak for this purpose. The dilution they mention is 1+9, although they state that it isn't critical. Compared to an untoned print, there might be a slight, but even stain, which might be more difficult to spot, but its there.

Click to expand...

NB23 said:

I agree that a stain will appear, but not instantly. Over time, a print will start talking about how archival it really is. But that takes time and exposure to air. That's my own theory based on the actual theory.

I have never had this staining happen to me, even when I was sure I underfixed a print and then selenium toned it. However, I've had well fixed prints show stains and that was clearly because the print was not well rinsed and still had a good amount of fixer on it which reacted with the selenium.

Click to expand...

Kodak's recommendation to use selenium toner as an alternative to the ST-1 test for residual silver as described in Tech Pub. J-1 (p.41):

"Testing with KODAK Rapid Selenium Toner

If you wish to use a more stable reagent than KODAK Residual Silver Test Solution ST-1, you can use a dilute solution of KODAK Rapid Selenium Toner to test whether prints are thoroughly fixed.

To use, dilute one part of KODAK Rapid Selenium Toner with 9 parts of water. The proportions are not critical. Using this solution, follow the directions given above for the use of KODAK Residual Test Solution ST-1.

NOTE: This test fails where a very large excess of hypo is present, as in stabilized prints."

The test method described is the drop method, the same for ST-1, which is:
1. Place a drop of the diluted solution on a squeegeed, white margin of a print or a clear part of film.
2. Wait two to three minutes; then wipe off the drop with a clean blotter or cloth.
3. Any yellowing of the test spot other than a barely-visible cream tint indicates the presence of silver. (That means: Refix)

Worth distilling from this is that a working solution of selenium toner will not give an accurate test result when the print is transferred directly from the fixing bath to the toning solution (my practice). You need to do the test on a well-washed print.

And, although the stain doesn't appear "instantly," it does after two to three minutes if there is excess residual silver in the print. Sorry NB23, but Anon Ymous has it right.

For those interested, J-1 is available here: http://www.bonavolta.ch/hobby/files/Kodak j-1.pdf

Best,

Doremus

Doremus Scudder said:

Kodak's recommendation to use selenium toner as an alternative to the ST-1 test for residual silver as described in Tech Pub. J-1 (p.41):

"Testing with KODAK Rapid Selenium Toner

If you wish to use a more stable reagent than KODAK Residual Silver Test Solution ST-1, you can use a dilute solution of KODAK Rapid Selenium Toner to test whether prints are thoroughly fixed.

To use, dilute one part of KODAK Rapid Selenium Toner with 9 parts of water. The proportions are not critical. Using this solution, follow the directions given above for the use of KODAK Residual Test Solution ST-1.

NOTE: This test fails where a very large excess of hypo is present, as in stabilized prints."

The test method described is the drop method, the same for ST-1, which is:
1. Place a drop of the diluted solution on a squeegeed, white margin of a print or a clear part of film.
2. Wait two to three minutes; then wipe off the drop with a clean blotter or cloth.
3. Any yellowing of the test spot other than a barely-visible cream tint indicates the presence of silver. (That means: Refix)

Worth distilling from this is that a working solution of selenium toner will not give an accurate test result when the print is transferred directly from the fixing bath to the toning solution (my practice). You need to do the test on a well-washed print.

And, although the stain doesn't appear "instantly," it does after two to three minutes if there is excess residual silver in the print. Sorry NB23, but Anon Ymous has it right.

For those interested, J-1 is available here: http://www.bonavolta.ch/hobby/files/Kodak j-1.pdf

Best,

Doremus

Click to expand...

Yes but we aren't talking about the same thing at all.

You are talking about testing a print while I am talking about the whole process of wet printing, from throwing light onto the paper to developing, stopping, fixing, rinsing, toning, rinsing, hypo-clearing, washing for 1 hour, and then drying for 12 hours.

In my whole process, there won't be any yellowing showing up even if it's badly fixed (from an exhausted fixer bath, for example)

But I do agree that once tested, the print will show the yellowing caused by the test drop.

It's been informative and educational reading the replies prompted by my original question. I was unaware of the detailed information available from Ilford and have filed copies for future reference.

I don't normally use my fixing baths for that many prints, but I was doing a lot of work prints, none of which were intended to be (or are) "final". Just for giggles I took what I knew to be the very last print I made and did a residual silver test in the margin using 1+9 KRST for 3 minutes per the Kodak publication as quoted by Doremus. There's zero discoloration visible after blotting, at least on the wet print. It's on the screen now after being rewashed and I'll check it again in the morning.

I guess this is a testament to two-bath fixing. But after such abuse I decided to dispose of both baths and start again fresh.

NB23 said:

Yes but we aren't talking about the same thing at all.

You are talking about testing a print while I am talking about the whole process of wet printing, from throwing light onto the paper to developing, stopping, fixing, rinsing, toning, rinsing, hypo-clearing, washing for 1 hour, and then drying for 12 hours.

In my whole process, there won't be any yellowing showing up even if it's badly fixed (from an exhausted fixer bath, for example)

But I do agree that once tested, the print will show the yellowing caused by the test drop.

Click to expand...

A badly fixed print (i.e., with too much retained silver) will discolor upon toning in selenium toner, either staining in blotches or acquiring an overall yellowing. In fact, Ilford's toning brochure, mentioned above states the following:

"Instant test of adequate fixing
Prints that are not fully fixed will show staining when transferred to a toning bath."

I can confirm this from personal experience. However, if you're using a very dilute toner, maybe the yellowing won't be so noticeable. Also, if you don't tone, then, of course, you won't see discoloration for some time, till the retained silver starts to react with pollutants in the atmosphere.

Hence the need for testing.

Best,

Doremus

I use the same method with fixer as I do with RA4 Chemicals.

I use an open dish for the developer, but to save space the stop bath and fixer is held in a 12x6 Nova deep tank processor, maily to save space. For every 80sq inches of paper (a 10x8 print) I replenish the fix with 10cc of fresh fixer. The stop bath I change as soon as I notice a change in colour. Using this method may be a bit over the top with regards to the fixing stage, but it ensures that I never have a print that is not properly fixed.