Brownish mottling/staining on my fiber prints after selenium toning

The last couple of prints I made, I noticed a slightly brown mottling or staining on the paper, especially in the white areas such as the totally unexposed print border. I suspect it's everywhere, just most noticeable in the white areas because it's not competing with darker tones or image detail. This has happened on both an 8x10 and an 11x14 print now, from different boxes purchased at different times, so I don't think it's the paper to blame. After the prints with this mottling have dried, the paper has a gritty texture that seems to brush off with some effort, but the staining remains.

Here is my process for making a final print (after test strips, etc. have been worked out):

1. Expose paper in easel (I use exclusively Ilford MG FB, standard/neutral tone, not warm or cooltone)
2. Develop 2 minutes in Ilford MG developer 1:14, gently agitating the tray throughout
3. Water stop for 1 minute
4. Fix in TF-5 for 4 minutes
5. Hold in water bath for anywhere from 2 minutes to ~1 hour, depending on how many other prints I'm doing during that session
6. Quick rinse in running water for about a minute
7. Tone in Kodak Rapid Selenium Toner 1:19 for 5 minutes, agitating gently throughout. I've been using the same 1 gallon jug of 1:19 working solution toner for several months, but I'm a fairly low volume printer and still getting a tone that I'm happy with. I have my toner mixed in plain water, not any kind of wash aid. That said, it was at this toning step where the brown mottling appeared on both prints where I saw it, so I assume something is wrong with my process surrounding toning, or perhaps just my toner itself.
8. Wash in Kodak Hypo Clearing Agent for ~2 minutes
9. Final wash in running water for 20-30 minutes

I have tossed the gallon jug of working strength toner and will mix up some fresh stuff, but I don't understand why the toner would have started doing this. Theoretically if it was exhausted, shouldn't it just have stopped giving any noticeable effect to the print? I probably have something like 25 or so 8x10 sheets of fiber paper through this gallon of toner.

My only other guess is that the fixer needs to be washed off more thoroughly before toning? Does leftover fixer interact with selenium toner? Seemed like a waste of water and time to do a complete wash after fixing and then again after toning, but if it's the right way to process a print then I'll do it.

My most recent one is drying right now, so I'll post a picture of the mottling when I get a chance tomorrow.

BHuij said:

My only other guess is that the fixer needs to be washed off more thoroughly before toning?

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That's the first change I would make, indeed. Your holding tank is basically a very dilute fixer in which you keep the prints. If you only rinse briefly after that, there will be significant traces of silver-thiosulfate complexes in the paper, and they may interact with the toner. I'd propose to give the prints a couple of consecutive washes in clean water and long enough (let's say at least 2 minutes per wash) to displace the dirty holding bath water.

A few months ago I had the same issue: brownish stains on the white borders of a FB print.

After some, stumbling around, searching, reading, testing, trial and error; all the sudden I remembered that Kodak used Selenium in a mixture to test the fixing quality of a print (and film). Testing if there ware stil some unused (unexposed thus undeveloped-) silver halides left in the emulsion after the fixing bath by showing colouration changes.
So this was actually a fixing procedure test: checking the status of the chemicals and how the it was done, and if bad, unfixed silver is left in the emulsion and colouring yellow-brownish when treated in Selenium.
One can consider Selenium toning as a fixing test, till a certain extend although...

But my fixing bath was rather fresh, the only thing I did wrong was a bad agitation of that print as I was distracted by a cell-phone call.
As a print tend to float, the white borders are close to the surface, even emerging, and by this even more badly fixed.

I could save the print by bleaching the white borders with 2% Kaliumhexacyanoferraat(III), and fixing the whole print there after, but I just wonder how long that print wil last...

BTW, I give, after a short rinse, a 2% Sodium Sulfide Sulfite bath for 2 min. before Selenium toning.
Then I apply the Ilford water saving print washing procedure.

Philippe-Georges said:

after a short rinse, a 2% Sodium Sulfide bath for 2 min

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Sodium sulfite !!
Otherwise brown stains are guaranteed...

You're right that insufficient fixing is also a risk factor, but 4 minutes in TF-5 should preclude this - assuming the TF-5 isn't overused or over-aged.

koraks said:

Sodium sulfite !!
Otherwise brown stains are guaranteed...

You're right that insufficient fixing is also a risk factor, but 4 minutes in TF-5 should preclude this - assuming the TF-5 isn't overused or over-aged.

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Yes, I wrote it wrong, it must be Na2SO3.

I bet it was fixer exhaustion. I was over 50% of the capacity of the batch of fixer (hence the longish times for TF-5). I also tossed that after last printing session because I suspected it was getting depleted.

In short, fresh fixer and a much more thorough rinse prior to toning should sort this out. Any reason not to use hypo clearing agent prior to the toner? If I do, will I still need to use it again after toning and before the final wash? HCA is one of the cheaper chemicals in the process so I don’t mind using it twice if it will speed things up and save water.

BHuij said:

I bet it was fixer exhaustion. I was over 50% of the capacity of the batch of fixer

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Ahhh.
In general, I would recommend against reusing fixer across multiple sessions and be very conservative in using its capacity.

BHuij said:

Any reason not to use hypo clearing agent prior to the toner?

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No, not necessarily, but responding to your other question: you might indeed want to repeat it after toning due to the presence of thiosulfate in the toner itself.

A good way to guard against fixer depletion is to use two fixing trays. You fix in the first for a few minutes then move to the second for a few minutes. The first tray does most of the work. The second more or less rapidly eliminates the remaining silver. Once you hit capacity for the first, dump it and make the second the first - fill a fresh second tray.

Don Heisz said:

A good way to guard against fixer depletion is to use two fixing trays. You fix in the first for a few minutes then move to the second for a few minutes. The first tray does most of the work. The second more or less rapidly eliminates the remaining silver. Once you hit capacity for the first, dump it and make the second the first - fill a fresh second tray.

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That's what I do for years now, but, 'accidents' can still happen.
And 2% Na2SO3 is a simple hypo clearing agent.

Fixed your Sulfide/Sulfite oops for you.
Pun intended.

MattKing said:

Fixed your Sulfide/Sulfite oops for you.
Pun intended.

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That's what happens when you 'think' in Flemish/Dutch and have to write in English, different languages tend to mix, sometimes...

And to be clear:

Dat heb je nu eenmaal als je denkt in 't Vlaams/Nederlands en in 't Engels moet schrijven, talen hebben de vreemde gewoonte om zich soms te eventjes te vermengen...

Don't worry, no hard feelings.

Philippe-Georges said:

That's what happens when you 'think' in Flemish/Dutch and have to write in English, different languages tend to mix, sometimes...

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The Dutch for sulfite is sulfiet. Dutch for sulfide is sulfide. The difference is just as distinct in Dutch as it is in English.

koraks said:

The Dutch for sulfite is sulfiet. Dutch for sulfide is sulfide. The difference is just as distinct in Dutch as it is in English.

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Yes, you are right, that's why i wrote the formula in my last post, just to be sure...

I was being pedantic, my apologies
Including the formula was of course a very transparant thing to do!

FWIW, you might also help aid in preventing the staining if you switched from a water stop to a stop bath.
TF-5 is well buffered, so it works fine with an acidic stop.
And nothing speeds the deterioration of fixer like adding non-neutralized developer to the fixer.

If the paper is MG Classic, you need to be extra careful to quickly immerse the print evenly in each respective solution, and pay attention that it remains submersed, with no areas briefly floating above the solution. That applies to the fixer step too. Keep up consistent gentle fluid agitation over the whole area. An acid stop bath would certainly help in this case. MG Cooltone is fussy in the same manner; but MGWT is a lot more forgiving. Never re-use TF4 or TF5 fixer on another day; only use it fresh. No need for double-tray fixing or HCA.

In other words, I doubt your problem is fixer depletion. More likely, it's uneven fixing. But uneven dev could also be a contributing factor, especially when attempting to use plain water in lieu of a stop bath.

There are two main reasons why selenium toning will cause stains. The first is transferring the print from a too-acidic environment directly to the toner. This would happen, say, if you were using an acid hardening fixer with relatively low pH and moved the prints directly from that to the toner.

The second, and much more common, is toning a print that has not been adequately fixed. There are a number of reactions that happen during fixing that gradually change the unexposed silver halides into soluble compounds. There are several intermediate reactions that happen before solubility is reached. As fixer becomes more saturated with dissolved silver (in many forms) during use, this reaction chain slows down and, eventually, never runs to completion, leaving some of these insoluble intermediate compounds behind. These are what react with the selenium to cause staining.

The solution is obvious; just don't use your fixer beyond capacity. Nailing down the capacity is a bit trickier. The best way is to test with ST-1 or selenium toner 1+9 (or stronger) and find the limits of your regime. Then build in a safety factor and use throughput as a guide. Following the manufacturers' recommendations is also good.

However, there is often confusion about fixing standards. Fixing to what is often called "commercial" standards, or "general-purpose" standards is not as thorough as fixing to standards for "optimum permanence" or "archival." And, experts differ on exactly how many prints through the fix comprise these two standards. What is clear is that dissolved silver in the fixer cannot exceed a certain level before it starts leaving some insoluble compounds behind.

Here's Ilford's take: "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, ... 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 ... 8 x 10in prints." [Emphasis added] (Ilford tech sheet on Rapid Fixer, p 4).

They then talk about throughput and testing prints.

Note that for a single-bath fixing regime and optimum permanence, you can only fix 10 8x10s per liter of fixer (this regardless of fixer dilution since it's the amount of dissolved silver in the mix that makes the difference, not the fixer strength). When you approach the capacity limit for the "commercial" standard of 40 8x10 prints/liter the risk of having insoluble silver compounds left in the paper is quite high (especially if you've been fixing a lot of high-key prints). It's at this point that staining in the toner will become a real risk. This is what I believe happened in your case.

A two-bath fixing regime (as mentioned above) will help in two ways. First, it's more economical. Since the bulk of the reactions take place in bath one, bath two really just finishes things up and remains fairly fresh. This allows you to run approx. 40 8x10s through a liter each of bath one and bath two (total 20 8x10s per liter) and effectively double the capacity. If you promote bath two to bath one when that throughput has been reached and mix a fresh second bath, economy is even greater.

Second, and perhaps more important when you're toning, is that bath two rarely has much dissolved silver in it, since most of that ends up in bath one. Therefore, you are more certain of fixing to a higher standard with a two-bath regime and, if you keep an eye on throughput, rarely ever end up toning prints that are under-fixed.

Bottom line: be aware of fixer capacities for whatever method you use and toss the fix well before exhaustion.

And, as Drew mentions, be sure you're immersing your prints quickly and completely in all solutions and keeping them well-agitated and below the surface (tongs or gloved fingers are great for pushing down the print). I usually lay the print onto the top of the solution face-down, press the print slowly to the bottom of the tray and then pick it up and flip it, re-submerging it gently. I don't like tray rocking alone for agitating; I gently move the print around and press down the parts that float up in turn. I'll often lift the print out of the solution and flip it a time or two during processing as well.

Best,

Doremus

Regarding fixer capacity - I usually do a strip test with the paper I'll be printing on, and when 45-60 seconds of fixing still leaves any yellowing from the developer, that fixer becomes bath one and I make a fresh bath two. Then I test bath 2 each session for 45-60 second exhaustion (and I consider that 45-60 time to be minimal and I'll double it, and I have the extra kickstart of bath one). I can't really think of a better way to test the fixer itself. My fix bath two lasts quite a long time with 2-bath fixing.

Even with 2-bath fixing, doing proper washing, HCA, and testing with RHT, my prints test clean after about a 20 minute wash; I use slightly warm wash water which really does speed up the diffusion of fixer from the paper.

MattKing said:

FWIW, you might also help aid in preventing the staining if you switched from a water stop to a stop bath.
TF-5 is well buffered, so it works fine with an acidic stop.
And nothing speeds the deterioration of fixer like adding non-neutralized developer to the fixer.

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Looks like good advice to me.

I know that stop bath has been fully debated recently here. All I can suggest is that an experiment is in order if you have staining with expensive and labour intensive FB prints.

I used running water "stop" but still sometimes got some staining that took time to appear. Now I use an acid stop and the problems have gone away.

I use metabisulphite buffered to pH around 5.5 with a little sodium hydroxide so it smells less than straight metabisulphite and has higher capacity. It still smells of SO2 so recommended only if you have ventilation. I have a theory that it is very compatible with neutral fixer.

As we are debating stop bath (again) I would like to advocate the use of a buffered stop bath, what I do for nearly 20 years now.

It's not only interesting when processing film in staining developers, but it's very useful in all the kinds of developing processes, film as well paper, particularly when a neutral-to-alkaline fixer is applied, as to keep everything nearly at same pH value.
It can also be replenished which means that there is less waste of a used plain vinegar stop bath.
A buffered stop bath can last for about an average of 6 months (mine does) when replenished systematically with 2% diluted acetic acid to compensate for the carry over by the developer.

I mix 5l per batch and keep half of it as a stockpile, which it does for a surprisingly long time.

The one I use has originally been formulated by Ryuji Suzuki.
I include this 'workflow' as an attachment, so you are free to do with it whatever you want, but if you want to mix it yourself then carefully read the warnings!

PS: Please do forgive me my spelling mistakes and sloppy English!

Philippe-Georges said:

buffered stop bath

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Any acetic-acid based stop bath will become a buffer upon use. Citric acid as well btw.

koraks said:

Any acetic-acid based stop bath will become a buffer upon use. Citric acid as well btw.

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Yes, but replenishable?

Philippe-Georges said:

Yes, but replenishable?

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Of course. Why on earth wouldn't it be??

The Ryui Suzuki stop bath simply adds hydroxide to acetic acid, forming an acetate buffer. If you add developer to an acetic acid solution, the hydroxide (which is there as a result of partial hydrolysis of carbonate; it's a weak base instead of a strong one like NaOH, but it still liberates OH-) will form the same acetate buffer. It will be less controlled, starting at a low pH and then creeping upwards as the buffer kicks in, but as the stop bath is used a few times, it will end up pretty similar as the one you use, especially if you re-use and replenish over several sessions. Replenishment would be with big-brand stop bath concentrate or an appropriate acetic acid/vinegar solution. Of course any indicator dye, if present, won't be reliable anymore due to the buffering action.

So you could just start with any old stop bath, use it, replenish it as you see fit, and you'll have the same buffered, replenished stop bath that you're using. It will also be just as contaminated with halides, dyes etc. that leach from the film and/or paper as your concoction. These contaminants likely wont hurt the fixing process (much), but they could contribute to staining or problems with toning if you use this for paper. I'd also be wary of using the same replenished stop bath for film, paper and color work; I wouldn't be surprised if problems arose from this.

The alleged benefit of this buffered stop bath, i.e. that it would somehow protect the stain when staining B&W film developers are used, is IMO a red herring as the statements that an acid stop bath would somehow interfere with stain formation are AFAIK not substantiated by any evidence. Indeed, those who have worked with staining developers in combination with acid stop bath or fixers have to my knowledge never noted any problems - I sure haven't.

The cost argument is of course a weak one given the marginal cost of big-brand stop bath or household vinegar.

In short, there are in my view no legitimate advantages to a replenished, buffered stop bath, and at worst there are some minor disadvantages (contamination, storage space). I personally see no merit whatsoever in risking any problems just to save a few cents on an annual basis...It's a solution (pun intended) in search of a problem.

BHuij said:

I bet it was fixer exhaustion. I was over 50% of the capacity of the batch of fixer (hence the longish times for TF-5). I also tossed that after last printing session because I suspected it was getting depleted.

In short, fresh fixer and a much more thorough rinse prior to toning should sort this out. Any reason not to use hypo clearing agent prior to the toner? If I do, will I still need to use it again after toning and before the final wash? HCA is one of the cheaper chemicals in the process so I don’t mind using it twice if it will speed things up and save water.

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I too put the prints in a water bath tray after fixing, but I don't rinse the prints at all before toning in the Kodak Selenium toner. I have seen it recommended to only tone directly after the fixer, or after properly rinsing the prints, but have never had any problems with the water bath. I only start with fresh fixer and don't make many prints at a time, so I think you are right about your fixer being exhausted.

Kodak Rapid Selenium toner does contain Ammonium thiosulfate, but I guess not enough to complete the fixing.

All of the above explanations are valid and very informative. That being said, certainly more time should be given to washing prints before applying any toner. Never used Kodak’s toner because I made my own. I put prints in very large trays using old Kodak washing siphon and move prints about every now and then. This is the only part of development process where watching darkroom timer not required. Have a beer and listen to some music or take a nape.