Question about Hypam/rapid fixer capacity

As I’m preparing a massive printing marathon, I’ve decided to read Ilford’s Hypam instructions.

A few things Have struck me.

For RC paper; 1 liter of working dilution (regardless wether 1:4 or 1:9) will fix 80 8x10 prints.

30 seconds fixing time for 1:4 and 60 seconds for 1:9

My questions:

This is awkward. How can a 200% diluted solution have the same capacity as a regular dilution?

Supposedly, by doubling the fixing time, 80 prints will be effectively fixed BUT if I double the fixing time of a 1:4 bath, I wouldn’t be able to reach 160 prints, according to the literature. But plain regular logic would dictate otherwise.

There is clearly something wrong here.

Can someone shed some light on the true Hypam capacity per Liter of working solution (1:4 and 1:9)?

I also doubt the 80 prints per liter figure.

Thanks

Fixer is exhausted by buildup of silver in the chemical, before the chemicals actually stop working. Silver builds up at the same rate no matter the dilution.

I, too, would not put 80 8x10 prints in a liter. I'd probably do no more than 20.

chriscrawfordphoto said:

Fixer is exhausted by buildup of silver in the chemical, before the chemicals actually stop working. Silver builds up at the same rate no matter the dilution.

I, too, would not put 80 8x10 prints in a liter. I'd probably do no more than 20.

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i don’t quite understand... the buildup should be twice less in the 1:4 dilution. Otherwise we would be using 1:100.

There is obviously something I don’t understand.

Yeah, around 20 8x10 fb print per liter is about my psychological limit.

NB23 said:

There is obviously something I don’t understand.
Yeah, around 20 8x10 fb print per liter is about my psychological limit.

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When I mix some fresh fixer (whether for paper or film) I perform a clip test: how long does it takes to clear a piece of undeveloped film (keep same type to be consistent; do not switch from classical to/from T-grain). And I affix on the bottle, not only the date of mixing, but the clearing time. When the clearing time has doubled, dump. If fixer is used for film, fix for at least twice the current clearing time with the actual film processed.
No psychology involved. Peace of mind.

NB23 said:

...
My questions:
How can a 200% diluted solution have the same capacity as a regular dilution? Supposedly, by doubling the fixing time, 80 prints will be effectively fixed BUT if I double the fixing time of a 1:4 bath, I wouldn’t be able to reach 160 prints, according to the literature. But plain regular logic would dictate otherwise. ... I also doubt the 80 prints per liter figure.

Click to expand...

First, the difference between 1+4 and 1+9 isn't 200%... It's 50%; the weaker solution is half as strong.

But, to answer your question, it's not the strength of the solution that determines when the fixer is exhausted, but the amount of dissolved silver compounds that come from your paper. The strength affects the speed of fixing; you'll have to fix longer with the weaker solution. Still the fixer is ready to be discarded when the throughput capacity is reached regardless of the strength.

What happens is that as you fix the paper/film, the undeveloped silver gets converted into soluble compounds by the fixer and these dissolve out into the fixer solution. When there are enough of these compounds in the fixer the dissolved silver content reaches a point where it stops the fixing action of the fixer. For RC papers, that's around 8g/liter or so (similar to film). For fiber-base papers, the range is from about 2g/liter to 0.5g/liter depending on how long we want the print to last (see below).

If you read the Ilford tech sheet on Hypam/Rapid Fixer carefully you'll find out a few more things about capacity. It's here if you don't have it: https://www.ilfordphoto.com/amfile/file/download/file/1833/product/711/

In the first section on capacity on p.2, Ilford gives 80 8x10 RC prints per liter of fixer and 40 8x10 fiber-base prints per liter. So, if you only use RC paper, just follow their throughput recommendations and you'll be fine (no need to doubt Ilford's researched capacity numbers here).

For fiber-base prints, however, the plot thickens if you read further to page 5 and the section on Silver Concentration, you'll see that for fiber-base prints there are two "standards," "commercial" and "optimum permanence." For the latter, the capacity of a single-bath fixer is reduced to about 10 8x10 fiber-base prints per liter. That's pretty low, so they recommend two-bath fixing to increase the performance of the fixer.

All this is in the tech sheet if you read carefully and put 2 and 2 together. FWIW, it took a while for me to get my head around the parameters for fixer capacity; it's not as straightforward as developer or other chemicals that just work to exhaustion.

Hope this helps,

Doremus

I’ve been putting 2 and 2 together but somehow doesn’t add up.

Please answer this:

A) For archival purposes, the 2-bath setup for 16x20 fiber prints, should they be 1:4 or 1:9?

B) Each bath 30 seconds or 1 minute? (For a dilution answered in A above)

C) For 3 Liters of working solution (from a dilution answered in A above) how many 16x20FB prints can be archival fixed?

D) after how many 16x20FB prints do I discard bath 1?

please note, I have all my personal answers but I need validation. Thanks

Doremus Scudder said:

First, the difference between 1+4 and 1+9 isn't 200%... It's 50%; the weaker solution is half as strong.

But, to answer your question, it's not the strength of the solution that determines when the fixer is exhausted, but the amount of dissolved silver compounds that come from your paper. The strength affects the speed of fixing; you'll have to fix longer with the weaker solution. Still the fixer is ready to be discarded when the throughput capacity is reached regardless of the strength.

What happens is that as you fix the paper/film, the undeveloped silver gets converted into soluble compounds by the fixer and these dissolve out into the fixer solution. When there are enough of these compounds in the fixer the dissolved silver content reaches a point where it stops the fixing action of the fixer. For RC papers, that's around 8g/liter or so (similar to film). For fiber-base papers, the range is from about 2g/liter to 0.5g/liter depending on how long we want the print to last (see below).

If you read the Ilford tech sheet on Hypam/Rapid Fixer carefully you'll find out a few more things about capacity. It's here if you don't have it: https://www.ilfordphoto.com/amfile/file/download/file/1833/product/711/

In the first section on capacity on p.2, Ilford gives 80 8x10 RC prints per liter of fixer and 40 8x10 fiber-base prints per liter. So, if you only use RC paper, just follow their throughput recommendations and you'll be fine (no need to doubt Ilford's researched capacity numbers here).

For fiber-base prints, however, the plot thickens if you read further to page 5 and the section on Silver Concentration, you'll see that for fiber-base prints there are two "standards," "commercial" and "optimum permanence." For the latter, the capacity of a single-bath fixer is reduced to about 10 8x10 fiber-base prints per liter. That's pretty low, so they recommend two-bath fixing to increase the performance of the fixer.

All this is in the tech sheet if you read carefully and put 2 and 2 together. FWIW, it took a while for me to get my head around the parameters for fixer capacity; it's not as straightforward as developer or other chemicals that just work to exhaustion.

Hope this helps,

Doremus

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You have the Ilford fact sheet. Pretty thorough. You had a detailed explanation by Doremus Scudder.

I’ve understood all of the ilford fact sheet. But it still isn’t clear. Especially Doremus’ explanation is only repeating the fact sheet.

How can it be that a fixer solution can be Replenished by adding a little bit of fresh fixer into it, and yet a dilution with TWICE MORE fixer in it (yes, DOUBLE; 1:4 vs 1:9) doesn’t increase in capacity. So, what do you have to say about this?

Sometimes there are mistakes or oversights in datasheets. See e.g. the notorious mistake of Kodak concerning "new" 400TX in HC-110 dil B: an obvious mistake, they never acknowledged or corrected it.
As far as I'm concerned, I do not go by the rated paper area per litre of working solution. I do a test clip at the beginning of each printing session and discard fixer when clearing time has doubled from initial value; As i wrote above in post #4. I hope this answers your question about capacity.

Test clips are valid for film only. Paper is impossible to tell.
Also, test clips don’t tell the whole story. It can clear a film but it says nothing about the long run. Archival? who knows, if the fixer is old. Even though it cleared the film.

Looks like Doremus has no answer to give except to repeat a fact sheet that is “maybe erroneous”.

oh well.

NB23 said:

I’ve been putting 2 and 2 together but somehow doesn’t add up.
Please answer this:
A) For archival purposes, the 2-bath setup for 16x20 fiber prints, should they be 1:4 or 1:9?

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You can use either. Ilford recommends the stronger dilution and shorter fixing times (1 minute total) to keep the fixer from completely saturating the paper base and thereby make washing faster. Personally, I use the 1+9 dilution of Ilford Rapid Fixer or Hypam and longer fixing times (1.5 minutes in each bath). I find it difficult to keep fixing times to just 60 seconds with larger prints. Heck, it takes 15-20 seconds for a 16x20 print to drain... However, I treat with a wash aid and wash appropriately longer: 60 minutes minimum. So, the choice is up to you; whatever works well for your workflow.

NB23 said:

B) Each bath 30 seconds or 1 minute? (For a dilution answered in A above)

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Two bath fixing with the stronger dilution and keeping to Ilford's recommendation of 1 minute total would equal 30 seconds in each bath. Like I said, it gets dicey keeping the fixing time low and dealing with the drain time. I guess one could transfer from fix one to fix two without a drain and then from bath two to a water bath without a drain as well. I find the weaker dilution works better for me with two-bath fixing. I fix a bit more than the recommended two-minute total time Ilford recommends: 1.5 minutes in each bath. The extra minute of fixing is irrelevant once the paper is saturated. Fixing too long, however can bleach the image slightly, so try to stay around the recommended total time.

NB23 said:

C) For 3 Liters of working solution (from a dilution answered in A above) how many 16x20FB prints can be archival fixed?

Click to expand...

Note please, the dilution has no bearing whatsoever on the throughput capacity of the fixer! Dilution only changes fixing time!
Let me go through this from a one-bath starting point; bear with me.
With one bath fixing and processing for optimum permanence, the capacity of the fixer is approx. 10 8x10-inch prints per liter. With two-bath fixation, one uses two liters and the total capacity doubles. This means 40 8x10 prints for two liters of fixer divided into bath one and bath two. Another way to think of this is 40 8x10 prints per liter of bath one, but you need the fresh bath two to finish all those in. Now, after you've run 40 prints through both fixing baths, fix one is exhausted and should be discarded. Since fix two is still fairly fresh, it can be promoted (demoted?) to bath one, you can mix a fresh bath two, and you can start the whole cycle over again. Kodak recommends that this cycle (replacing bath one with bath two and mixing a fresh bath two) can go on for seven iterations. I never go more than five. Furthermore, I try to limit my throughput to 36 8x10s per liter of bath one (just because it works out better for me since I have a 12-print washer).
So, now, on to your situation: Three liters of fixing bath one and three liters of fixing bath two, for a total of six liters, has a throughput capacity three times that of one liter each of bath one and bath two. That's 3 x 40 = 120 8x10s per 3 liters of bath one.
A 16x20-inch print = 4 8x10-inch prints. So we divide 120 by 4 and get 30 16x20-inch prints per three liters each of bath one and bath two.
Clear?

NB23 said:

D) after how many 16x20FB prints do I discard bath 1?

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See above: 30 16x20s through three liters each of fix one and fix two is the upper throughput limit. At that point, you toss fix one, move fix two to the first bath position, mix a fresh second bath and start the process over again: you've got another 30 16x20s to fix before you have to toss bath one again.

Hope this clarifies things,

Doremus

Doremus, thanks!

This coincides with my own old notes, 10 16x20fb with 2 baths. I used to fix 14 20x24fb in 5 liters of 1:4 hypam and then discard, back when I used to print a lot of 20x24. Boy that was a pita... and yet, so satisfying.

Your explanation, such as Ilford’s, say that 1:9 vs 1:4 don’t matter as far as fixing capacity go. However, I’m a little bothered by that because a replenishment actually prolongs fixing capacity by simply adding more fresh fixer into the solution. Which, in truth, is nothing more than adding more concentration into the solution. So, with the replenishment theory, 1:4 should fix more prints than 1:9.

I also have one last question. I may be too stupid to understand (and I’m ok with that): why should we trash both baths after 7 iterations? Isn’t this an endlessly renewable cycle, where a fresh bath #2 is perpetually introduced?
I mean, the cycle is perpetually refreshed by a new bath and perpetually purged of a bad bath! Therefore why the need to specify that bath 1 should be discarded and a fresh bath should be made after 7 cycles? This actually happens after each single cycle!

Fixer replenishment is based on removing part of the fixer working solution and then replacing it with fresh (or making up for the loss due to carry-over). This automatically dilutes the fix back to a more usable state. However, I doubt that any fixer replenishment regime is really suitable for processing for optimum permanence... At any rate, large-volume mechanical processors that use a replenishment regime for the fixing stage need to be monitored for dissolved silver and the fixer adjusted accordingly. This isn't really a viable option for small-volume processors.

Again, the amount of dissolved silver in the fixer determines when it should be discarded, regardless of the dilution. I guess I should mention again as well that the fixer dilution affects the speed of fixation, but not it's capacity. The dissolved silver, as it builds up, starts to inhibit complete fixation. Depending on the completeness of fixation desired, the fixing bath can have anywhere from 10 g/liter dissolved silver (film/RC paper) to 0.5 g/liter or less (optimum permanence). "Commercial" and "general-purpose" standards are somewhere in between. Fiber-base paper really needs a more stringent standard since the paper fibers themselves collect unfixed or partially fixed compounds that may later discolor.

I use fiber-base papers and process for optimum permanence, so my choices are based on that. Two-bath fixing and using the weaker dilution get me the level of fixation I desire and fits my work-flow. I test my prints regularly for both residual silver and hypo (fixation and washing tests, respectively), so I'm confident my regime is working well.

There are many (including the late Ron Mowrey, aka PE here on the forum) who use one-bath fixing with short fixing times and simply discard the fixer after their throughput threshold is reached. That practice is completely viable. If I were to do this, I'd spend a bit more on fixer than I do now (not a huge issue) and be mixing new fix more often (a bigger issue for me). Still, there's nothing wrong with fixing 10 8x10-inch prints per liter in the stronger dilution for a shorter time and then just tossing the fix and mixing new. This would be especially applicable if water for washing was at a premium, since wash times could be kept much shorter.

My workflow, as already described, uses the weaker solution and two-bath fixation coupled with a longish treatment in wash-aid and a longer wash time. I'm more comfortable with this, especially with larger prints.

As far as the two-bath fixing cycle goes: The seven-cycle limit on moving bath two up to bath one is Kodak's recommendation. Their explanation is that dissolved silver builds up in both baths due to carry-over from the cycles before, and therefore the amount of dissolved silver carried over from the first to second bath is enough to keep the second bath from completely doing it's job as bath one if promoted. At that point, both baths should be mixed fresh. Kodak usually gives large safety factors, but seven changes seems generous enough; I don't have to push it. In practice, I rarely get to even four or five such cycles.

Best,

Doremus