Questions on Fog in Salt and Albumen Prints

I’d like advice on two issues with my recent salt and albumen prints.

1 — Fogging(pls. see the image)
Salt print (left) and albumen print (right) were made under identical conditions, with 5 minutes in gold-borax toner.
Only the margin outside the image was masked with Rubylith.
Paper: Hahnemühle Platinum Rag.
I’m seeing:
– Fog just above the image in the salt print
– Fog around the image in the albumen print

For the albumen print: silver nitrate solution was applied to a fully dried sheet, with two drops of citric acid. It dried in the darkroom for about 80 minutes, and some fog was already visible before exposure.
I toned those prints before fixing.

What are effective ways to prevent this fog?

2 — Fixing Time (for both processes)
Ellie Young recommends 8 minutes (two 4-min baths), but Christopher James suggests only 30–60 seconds.
In my tests, the 8-minute fix noticeably bleached the print.

I’d appreciate opinions on this large difference in fixing times.

Thank you!

For salt prints IME: Stronger fixer. Ammonium fixer instead of sodium. Thinner paper. Less (or no) gelatin. Floating instead of submerging.

I don't know if these changes will be relevant in your process though.

Yeah, this is a problem with these printing processes. It's super frustrating.

D_Quinn said:

I toned those prints before fixing.

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I find the only way to get really clean salt prints is to tone after fixing. I use a thiourea-gold toner which probably is part of the problem; a pure gold toner with no source of sulfide might work better. I don't know for sure; it's just a hunch. Anyway, try toning after fixing. It'll be easier that way.

D_Quinn said:

For the albumen print: silver nitrate solution was applied to a fully dried sheet, with two drops of citric acid. It dried in the darkroom for about 80 minutes, and some fog was already visible before exposure.

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The fact that you already get fogging before actual UV exposure suggests that the fog is chemical in nature; it might be due to sulfur compounds present in the albumen solution. Another issue is that albumen prints will be more difficult to fix properly because of the albumen layer which can more effectively trap unexposed silver compounds. This doesn't explain the pr-exposure fog, but can contribute to the fog that happens later.

Another thing to consider is to use a thinner paper; thicker papers easily trap silver salts that you want to fix & wash out of the print. The thinner the paper, the more effectively it will fix & wash out.

PS: the salted paper print shows fogging also around the other edges; not just the top. It's less apparent though, but it's there if you look closely. My bet is that you used a coating rod and the top of the print was the spot where you dropped the bead of solution and/or where you stopped coating; a little more sensitizer soaks into the paper at this point, resulting in a higher fog level.

I find that the only way to get clean salt prints is to:
* Avoid any UV and blue light exposure before the print is completely fixed
* Fix thoroughly; I use a rapid fixer like @FotoD mentions above
* Tone after fixing and after rinsing the print for a few minutes
* Wash the print thoroughly, allowing for several changes of the wash water.
Even then, it takes a decent amount of luck and one print may come out a little cleaner than another.

It's very, very difficult to get 100% clean highlights with salted paper.
I've not done enough albumen to make definitive comments only that I observed that adding albumen also adds complexity.

All of the salt prints on my website were fixed for 60-seconds, as recommended by Christopher James, and now, ten+ years later, exhibit zero fading. As he recommends in his book, I mixed ammonia or sodium carbonate in the fixer and never saw any degradation in the image during fixing.

@Tom Taylor what papers do you use, and do you mask the borders around prints? Do these borders remain free of any fog? Fading is not the primary concern. Its fogging of the white areas. It's easily overlooked in prints without masked borders.

D_Quinn said:

I’d like advice on two issues with my recent salt and albumen prints.

1 — Fogging(pls. see the image)
Salt print (left) and albumen print (right) were made under identical conditions, with 5 minutes in gold-borax toner.
Only the margin outside the image was masked with Rubylith.
Paper: Hahnemühle Platinum Rag.
View attachment 412147I’m seeing:
– Fog just above the image in the salt print
– Fog around the image in the albumen print

For the albumen print: silver nitrate solution was applied to a fully dried sheet, with two drops of citric acid. It dried in the darkroom for about 80 minutes, and some fog was already visible before exposure.
I toned those prints before fixing.

What are effective ways to prevent this fog?

2 — Fixing Time (for both processes)
Ellie Young recommends 8 minutes (two 4-min baths), but Christopher James suggests only 30–60 seconds.
In my tests, the 8-minute fix noticeably bleached the print.

I’d appreciate opinions on this large difference in fixing times.

Thank you!

Click to expand...

Are you adding any citric acid to the salt solution? Standard practice (is it or is it only mine, I can't recall) is citric acid concentration at half the concentration of silver nitrate. For example if your silver is 12%, then make salt solution at 2% salt and 6% citric acid (i. e. 2g salt + 6g CA in 100 ml water.) Citric acid is what restrains the formation of chemical fog. Somehow you are not getting getting enough of it in the paper.

:Niranjan

Thank you, everyone, for the valuable comments.
I’ll try the following points one by one:

• Using thinner papers
• Increasing citric acid, or acidifying with sulfamic acid
• Switching to an ammonium fixer
• Toning after fixing
  (I already saw slight fog even before exposure, but I’ll try this just in case)

About citric acid​

@nmp, I did use citric acid for both salted and albumen prints, but I now realize that the amount I used was far lower than what you suggested. I’ll try a stronger concentration next time.

For reference,
– My silver nitrate solution is 13.6% w/v
– My citric acid solution is 10% w/v
– Before coating, I added only two drops of the citric acid solution to 5 ml of silver nitrate.
Now I understand that this is far below the recommended level.

Albumen printing — papers​

I’ll also test thinner watercolor papers such as Canson Croquis XL (neutral).
In that case, would it be reasonable to treat the paper with sulfamic acid before applying albumen, or if I add citric acid directly to the silver solution, do I still need to acidify the paper?

Fixer​

I currently use 150 ml of 10% hypo with a small amount of sodium carbonate (about 0.1 g) to raise the pH to around 8–9.
If anyone has a reliable ammonium fixer formula, I would really appreciate it.
Is it possible to simply dilute a rapid fixer to make one?

Thanks again.

D_Quinn said:

I’ll also test thinner watercolor papers such as Canson Croquis XL (neutral).
In that case, would it be reasonable to treat the paper with sulfamic acid before applying albumen, or if I add citric acid directly to the silver solution, do I still need to acidify the paper?

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I suspect the problem with your albumen prints is really due to the albumen itself which may contain fogging (sulfur) compounds. Albumen contains sulfur; think of the rotten egg smell that albumen develops. Perhaps if you use very fresh albumen?

Also, the technique of acid-soaking papers is really intended to get rid of alkaline (carbonate/chalk) buffers. This is relevant for iron-based processes (Van Dyke, Kallitype, cyanotype etc.) since these buffers will create insoluble iron compounds. Salted paper and albumen are not iron-based processes and thus in principle insensitive to this problem.

D_Quinn said:

If anyone has a reliable ammonium fixer formula, I would really appreciate it.

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Use color C41 fixer. It's near-pH neutral and based on ammonium thiosulfate. Alternatively, see if you can purchase some ammonium thiosulfate, either in dry form or as a 60% solution.

D_Quinn said:

Is it possible to simply dilute a rapid fixer to make one?

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That should work, too. It may help to use a pH neutral rapid fixer to avoid bleaching of the prints.

Increasing the citric acid content of your silver sensitizer is a good idea; see if that works a little.

We have previously discussed a similar problem with salted papers.


This is my approach to fixing the issue.

I cannot confirm this with albumen prints. It is worth a try.

@koraks
Thank you again — your explanations are always very clear.

About the fixer: in Japan it’s difficult to get C41 color fixer for hobbyists, but I do have a liquid rapid fixer for B&W film/paper (similar to Ilford Rapid Fixer).
The instructions say 1+4 dilution, but that seems a bit strong for salted or albumen printing.
Do you think 1+4 is still appropriate?

Also, instead of gold toning, would Ag Guard (Fujifilm) be a reasonable option?
Fuji says it offers better image stability than gold toning without changing tone or contrast.
https://www.biccamera.com/bc/item/2023851/

@Herzeleid
Thanks for the link. This is very helpful!
I only noticed the fog this time because I masked the borders — I didn’t realize it was also affecting the image and making the highlights look dull.

D_Quinn said:

The instructions say 1+4 dilution, but that seems a bit strong for salted or albumen printing.

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Yes, that sounds a bit strong. I would go with 1+10 or even 1+20. Fix for a few minutes. You may want to neutralize the pH of this supposedly acidic rapid fixer by adding ammonia solution. If you have pH test strips or a pH meter, this will help you balance the pH around 7. It's not very critical; 6.5-7.5 should be fine, but it doesn't have to be very exact.

D_Quinn said:

Also, instead of gold toning, would Ag Guard (Fujifilm) be a reasonable option?

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I couldn't say as I'm not familiar with this product. As I understand, comparable products from Agfa (Sistan) or ADOX (a new version of Sistan) rely on very weak sepia toning to offer some protection of the metallic silver image. I don't know how effective this is with salted paper prints and whether it might result in a color shift. In any case, I cannot really imagine it will be anywhere near as effective as gold toning taken to completion. There's also an aesthetic factor at work; personally when I gold tone a salt print, it's because I prefer the more neutral/cool hue of the print. It depends on the toner formula used, of course.

I think @Herzeleid's linked post is very interesting and certainly worth a shot. The extensive wash before fixing (or pre-fix toning) is indeed quite essential; whether or not it involves a chloride solution is perhaps (IMO) less important than the duration of that initial wash. Then again, the further discussion makes a plausible case for the use of ammonium chloride specifically. What I find also interesting is his mention of fogging with thiourea gold toner if it's done before fixing; I never read (or remembered) this, but it matches with my experience very well indeed.

koraks said:

Also, the technique of acid-soaking papers is really intended to get rid of alkaline (carbonate/chalk) buffers. This is relevant for iron-based processes (Van Dyke, Kallitype, cyanotype etc.) since these buffers will create insoluble iron compounds. Salted paper and albumen are not iron-based processes and thus in principle insensitive to this problem.

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Wouldn't Silver Nitrate react with Calcium Carbonate to form Silver Carbonate?

Raghu Kuvempunagar said:

Wouldn't Silver Nitrate react with Calcium Carbonate to form Silver Carbonate?

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The question is to what extent this happens and what happens afterwards with the silver carbonate. I couldn't say, really, other than that I don't see much evidence of this in the prints I've made. The fog seems (as in the investigation by @Herzeleid) to be exacerbated (in my case/experience) by UV, suggesting it's AgCl. I don't think silver carbonate exhibits the same photosensitivity - but I haven't checked.

I prefer that the Citric Acid is mixed into the sensitiser. Some people keep them separate, as the Citric Acid will leach out eventually. I mix a small batch (25ml) and it gets used up pretty quick, so I don't see this.
Print gets a good rinsing in Citric Acid laced tap water.
I fix in same fixer recommended by Christopher James for Kallitypes for one minute (combo of Sodium Thiosulfate & Ammonia)
Really thorough rinse in tap water, and letting print float face down for 15 min, followed by 5 changes of water.
Toned in Thiourea-Gold toner. I found that toning with this toner before fixing, resulted in fog.
For washing, I use the Ilford method, with a few periods of the print floating, face down.

Thiourea is part of odorless sepia toners. Ilford IT-6, if I recall correctly. Thiourea is a fogging agent. It fogs any remaining silver inside the paper fibers.
Toning before fixing does not cause any issue with vandyke brown in my experience. I assume initial washes are enough to remove iron and silver from the paper.
Prolonged washing before fixing salted paper is crucial, in my opinion. Especially multiple salted washes.
However, the solubility of silver chloride is dramatically different in ammonium chloride compared to sodium chloride. That is why I switched to ammonium chloride, and I am happy with the results.
I assume it is likely that a concentrated ammonium chloride solution can also remove other silver salts from the paper. Due to ammonia ions in the solution. Ammonia solution is the best solvent for silver salts.

Did you try washing the unfixed, but exposed print in a plain ammonia solution (i.e. no chloride)? Yes, it stinks...but I was wondering if that should work as well. As you said, silver chloride dissolves (to an extent) in ammonia.

koraks said:

Did you try washing the unfixed, but exposed print in a plain ammonia solution (i.e. no chloride)? Yes, it stinks...but I was wondering if that should work as well. As you said, silver chloride dissolves (to an extent) in ammonia.

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No, I didn't, that would stink horribly. Historically, ammonia solutions were the first attempt at fixing images used by Hercule Florence. Ammonia and silver salts form soluble compounds together.

Raghu Kuvempunagar said:

Wouldn't Silver Nitrate react with Calcium Carbonate to form Silver Carbonate?

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It actually does and it is photosensitive all by itself without the need for sodium chloride. One can coat silver nitrate on a buffered paper and expose and get an image, albeit at a slower speed. Check out my thread about Salt-free salt process.


:Niranjan.

@koraks Thanks for the suggestions and insights. I’ll follow them and see if this resolves the issue.

koraks said:

The question is to what extent this happens and what happens afterwards with the silver carbonate. I couldn't say, really, other than that I don't see much evidence of this in the prints I've made. The fog seems (as in the investigation by @Herzeleid) to be exacerbated (in my case/experience) by UV, suggesting it's AgCl. I don't think silver carbonate exhibits the same photosensitivity - but I haven't checked.

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That's interesting and goes against the advice given by some experts. Whatever works for you.

I consulted a couple of well-known references for Salt Printing and they recommend either avoiding buffered papers or acidifying them.

Quoting from Ellie Young's The Salt Print Manual:

"Fillers and loadings. Mineral pigments bind the fibres together, filling between the gaps creating denser sheets. These include calcium carbonate (acid buffer), China clay (kaolin), titanium dioxide and optical brighteners. Avoid these as they react with the silver nitrate before exposure, creating chemical fogging."

"RISING STONEHENGE MACHINE MADE (English) 245gsm NOT 100% cotton, buffered with calcium carbonate. Inexpensive paper. The calcium carbonate is problematic with the sensitivity of silver nitrate. This paper is absorbent, creating a dull print."

Quoting from Christina Z. Anderson's Salted Paper Printing:

"Some of the papers on today’s market are unsuitable for salted paper prints. One factor is calcium carbonate buffering which fogs the paper. The use of acids to either remove the calcium carbonate buffering or render it neutral has been common.."

nmp said:

It actually does and it is photosensitive all by itself without the need for sodium chloride. One can coat silver nitrate on a buffered paper and expose and get an image, albeit at a slower speed. Check out my thread about Salt-free salt process.

Salt-Free Salt Print Toned with Himalayan Black Salt

MODERATOR's NOTE: This thread evolved as it grew, and it became clear that it would be useful if some of its content were to be moved into a new thread. That work was done and the resulting thread is here...

www.photrio.com

:Niranjan.

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Thanks for confirming Niranjan. Nice print and lovely Kala Namak toning.

@koraks: No idea about fogging, but presence of Calcium Carbonate in the paper does definitely deplete the amount of Silver Nitrate available and thereby reduces both the speed of print-out and DMax. Silver Nitrate needs to be in certain excess over Silver Chloride for printing-out to be efficient as it reacts with Chlorine that's formed during the photoreduction of Silver Chloride to form more Silver Chloride and thereby increasing the availability of the latter for photoreduction. BTW this is also the reason why photographic papers (Chlrobromide) that take several hours/days to form an acceptable print in Lumen process produce prints with greater DMax and contrast while requiring significantly shorter exposure when coated with Silver Nitrate.

I am not entirely convinced that the paper buffer is the primary cause of fogging with salted paper prints. Since silver carbonate is also soluble in ammonia solution. The presence of ammonia in the fixer would address the issue.

Also, we would have observed an inconsistency, especially when ammonium chloride is used for paper salting/sizing.

Ammonium chloride reacts with calcium carbonate and produces calcium chloride, carbon dioxide, and ammonia. If the paper is dipped into the salting sizing solution, that would be enough to convert all calcium carbonate to calcium chloride.
So, any buffered paper that is salted with ammonium chloride becomes salted paper with calcium chloride in it.
There would be no conversion with sodium or potassium chlorides.
We would have observed a dramatic difference in behavior between these salting/sizing solutions.

@Raghu Kuvempunagar thanks for digging up those references. I don't doubt there can be problems associated with calcium buffers in papers - but at the same time, I get good results on heavily buffered papers without pre-treatment, provided I do the process right. @Herzeleid offers some good diagnostic insight IMO. I would like to add that even if a paper is buffered, this does not automatically mean that the buffer is chemically readily available to the silver nitrate to form silver carbonate etc. The sensitizer esp. with salted paper remains pretty much on top of the paper during sensitization and exposure due to the insoluble nature of silver chloride. You're probably right about the excess of silver nitrate, which could potentially participate in the formation of silver carbonate, but only if it penetrates deeply enough to link up with the carbonates of the buffer. The extent to which this happens depends a lot on the physical makeup of the paper, rheology, the method of applying the different parts of the sensitizer, the use of surfactants or binders, etc. I.e. it will be highly dependent on the specific parameters with which the process is being performed.

While I readily accept the vast experience of Young and Anderson, I'm hesitant to take their chemical hypotheses for gospel. Sorry to be somewhat skeptical in this regard. To the best of my knowledge, neither has performed the empirical research to test the hypotheses they state and they remain assumptions about what may be going on w.r.t. fogging. I personally think the mechanisms involved are more pluriform and more complex.

D_Quinn said:

If anyone has a reliable ammonium fixer formula, I would really appreciate it.

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You can mix rapid fixer with an alkali to make it neutral/alkaline. I've had success with 2+2 min of:

1+4: 800ml water + 200ml Fomafix + 12ml 25% NH3 (pH 7-7.5)
or
1+9: 900ml water + 100ml Fomafix + 6ml 25% NH3 (pH 7-7.5)

Thicker papers needed 1+4 to avoid fog. COT160 managed with 1+9.

Herzeleid said:

I am not entirely convinced that the paper buffer is the primary cause of fogging with salted paper prints. Since silver carbonate is also soluble in ammonia solution. The presence of ammonia in the fixer would address the issue.

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Are you ruling out dark reaction of Silver Carbonate especially in the absence of Citric Acid?

Herzeleid said:

Ammonium chloride reacts with calcium carbonate and produces calcium chloride, carbon dioxide, and ammonia. If the paper is dipped into the salting sizing solution, that would be enough to convert all calcium carbonate to calcium chloride.

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This is a trick I too have employed in FerroBlend process for working with buffered papers. And it seems to work well for not so heavily buffered papers.

Herzeleid said:

We would have observed a dramatic difference in behavior between these salting/sizing solutions.

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Fair point if buffered papers were used in those tests.

Anyway, Christina has given a long list of potential causes for fogging in Salt Prints apart from buffer.