Salt (NaCl) as a fog reducer?

I want to do a little developer homebrewing, and my test films will be various degrees of expired.

I don't have a readily available source of KBr (not carried in health food stores here) or benzotriazole to reduce fog, but I found a passing mention in (there was a url link here which no longer exists) thread that table salt is also a fog reducer.

My question is, does it have to be regular iodized table salt, or can it be sea salt or a salt without the iodine? I ask because I normally use sea salt for the table these days, and don't seem to have any "regular" table salt around. I also have some coarse kosher salt, and I found some "Half Salt" - sodium chloride, potassium chloride, some silica, and potassium iodide by the ingredients. Will any of these work just as well?

If all else fails I can go buy some table salt, but I would rather use what I have on hand if possible.

Thanks!

Some months ago, I made a saturated solution (about 35%) of canning salt (refined, coarse NaCl, without additives) because I wanted to see if that will make any difference in print developers. Well, it didn't seem to restrain the action of the developer, even when I added quite a lot of it. The print tone didn't get warmer either, but I got a stain at the border. Anyway, NaCl is a silver solvent, like sulfite and will give finer grain in film developers (MIcrodol-X, Perceptol), but it's far weaker as a restrainer compared to KBr. The order is Cl - Br - I, and KI is a very powerful restrainer. So, I doubt that you'll get an effect, but if you wish to try, use canning salt.

Anon Ymous said:

NaCl is a silver solvent, like sulfite and will give finer grain in film developers (MIcrodol-X, Perceptol), but it's far weaker as a restrainer compared to KBr. The order is Cl - Br - I, and KI is a very powerful restrainer. So, I doubt that you'll get an effect, but if you wish to try, use canning salt.

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In order to see any restraining effect you would have to use an amount of salt which is far beyond its solubility. I remember reading once that it can be used with chloride printing papers like Azo.

There is another use for sodium chloride. The following formula is from "Improved 35 MM Technique" by Paul Jonas where it is called Competol. It uses sodium chloride to increase the salt concentration and encourage surface development and acutance.

Water .......................................750 ml
Metol ........................................ 3.0 g
Sodium sulfite, anhydrous ............. 30.0 g
Sodium chloride ........................... 30.0 g
Water tp make .............................. 1.0 l

Use full strength. The most effective temperature is 27 C. Development times are 6 to 13 minutes.

Sodium Chloride is not a restrainer for emulsions generally but it is a weak restrainer for pure Chloride emulsions such as used in some B&W and color papers. Table salt, if it contains Iodide, will act as a restrainer based on the amount of Iodide present, but not on the basis of Chloride.

PE

OK, table salt it is

Next question: my local store carries "Sifto" brand table salt, so I bought a box. On closer inspection, the ingredients list sodium thiosulfate right above the potassium iodide (which is the last ingredient). I'm assuming the sodium thiosulfate is used as a stabilizer of some sort, and there won't be much relatively. But, that's plain hypo, so any idea if it will it have any effect on film? Would it negate the restraining properties of the iodide?

The other major table salt brand in Canada, "Windsor", doesn't have the sodium thiosulfate, but does have a small amount of invert sugar as a stabilizer - would that be any better for my purposes?

It is the KI that is antifogging if anything does.

The hypo is probably at such a low level that it does nothing.

PE

mabman said:

I want to do a little developer homebrewing, and my test films will be various degrees of expired.
...
If all else fails I can go buy some table salt, but I would rather use what I have on hand if possible.

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If you want to homebrew, then you should use something that works. Potassium bromide (KBr) really works both with expired b/w films and b/w paper. In Germany it is easy to order via pharmacy. 100 grams costed less than 10 USD and the KBr is highly active in anti-fogging, so you need for instance only about 1 to 5 grams per one liter paper developer to have the desired anti-fog effect and for film it in the same region.

I used KBr with success on 20 to 25 year old paper. With 5 grams KBr in one liter paper dev the paper became much more white in the unexposed areas than without the KBr additive, although it became not as absolutely white as a piece of undeveloped and only fixed paper, but nearly as white and white enough to get good pictures with it.

With different sheet films I could also see a reasonable improvement.

The downside of the KBr addition is that the speed of both the paper and the film is reduced and the development time has to be increased in case of the paper, because the first traces of the picture in the dev tray appear later. If the dev time with the film should also be increased, unfortunately I don´t have in mind no more. The speed reduction is no problem with the paper, but could be problematic if you need the full speed of your sheet film for shooting.

Best,
Andreas

A49 said:

If you want to homebrew, then you should use something that works. Potassium bromide (KBr) really works both with expired b/w films and b/w paper.

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I would normally completely agree, but the point of my homebrew adventure is to see if mint tea works (it's supposed to), and with a similar philosophy to Caffenol - make developer out of local/household ingredients.

As mentioned, I can't get KBr here in pharmacies or health food stores, it's apparently not as widely used as in Europe. So, ordering it in defeats my purpose for this little experiment.

Use NaBr then! It is more widely used in North America.

PE

Hmm, NaBr appears to be used in pool maintenance. I will have to try it next time - developer has already been mixed up with the table salt and tested on a roll - worked OK

You must not use table salt or Kosher salt which contain other chemicals such as potassium iodide, anti-caking additives, etc. Use canning salt which contains no additives. If you cannot find canning salt then you will have to order sodium chloride from a chemical supply company.

Sodium thiosulfate when added to a developer can cause fogging.

As the person in the aforementioned thread who first reported using salt to reduce fog, I feel obligated to jump into the discussion here and see if I can contribute anything. I have attached an image which shows some samples of what I was referring to, and would be interested in anything people have to say about it.

Let me first of all clarify that this involved development tests with caffenol-C. As a relative "noob" to film developing I don't know if the particular quirkiness of caffenol has anything to do with the improvements I think I am seeing. But I can say that after going back and forth several times now - both with and without salt in the formula - the salt has always helped and is now part of my "standard" caffenol-C recipe. Maybe there would be no effect with "normal" developers?

The attached image is a snapshot of three developed strips of Acros 100 roll film on my light table. Each strip shows two 6x7 frames with an image of a home made test target (incorporating a step wedge) that I have used for film/developer testing. Each of these strips came from rolls souped separately using 450ml of developer in a 1-roll tank, and using my standard caffenol-C developer (plus or minus the salt, of course). The top strip was souped with 10ml of sea salt, the middle with 10ml of table salt, and the bottom with no salt.

The bottom two are probably the most interesting pair since these are actually from the same roll. I cut the roll in half and souped the one half in the developer with the table salt and the other without the salt. Aside from that difference the processing was exactly the same. The top strip is from my very first salt test, using sea salt. After that test I tried table salt and found that there wasn't really much difference between the two and have used table salt ever since. Since these tests, I have also found that 5ml of salt gives nearly the same result as 10ml, so that's the amount I use now.

For what it is worth, I have also pointed a spotmeter at these strips while sitting on my light table, as a kind of "poor-man's densitometer" measurement. What I found is that the transmission through the top two differ by only about 1/6 EV. This may or may not be significant since they were not from the same roll nor necessarily developed using the same regimen. However, the bottom (no salt) strip is 2/3 EV darker than the "with salt" sample.

So that's what I found anyway. I am happy to fill in any other details as needed. What do you think?

Normally, both Table Salt and Sea Salt contain Iodide, and Sea Salt contains Bromide.

Iodide and Bromide are antifoggants especially Iodide even at low levels.

So, unless you used non-Iodized salt, a rarity nowdays in the US, (unless you use Pickling or Kosher Salt) you unwittingly added an extra ingredient that is an antifoggant.

PE

Denverdad said:

The top strip is from my very first salt test, using sea salt. After that test I tried table salt and found that there wasn't really much difference between the two and have used table salt ever since. Since these tests, I have also found that 5ml of salt gives nearly the same result as 10ml, so that's the amount I use now.

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Thank you for sharing your experience. I like the idea to replace the KBr with normal table salt for the fog reducing. If you write 10 ml, then you mean 10 grams, right?

Best,
Andreas

Denverdad, does the table salt container give any information about the potassium iodide content in ppm?

I do not know if this will help you, but here is the description of sodium chloride from Steven Anchell's "The Darkroom Cookbook, Third Edition:"

"Synonyms: Carbonate of soda, common salt, Kosher salt, muriate of soda, rock salt, salt, sea salt.
Appearance: Colorless, transparent crystals or white crystalline powder.
Uses: In preparation of chloride emulsions; salting papers before sensitizing and before toning; in hypo alum toning formulas; also acts as a weak restrainer*. [Emphasis is mine.]
Substitutions: Sodium chloride is simply common table salt. However, in the United States, it is almost always mixed with iodine, [comma added**] and the iodine is variable in nature and amount. Therefore, if you wish to buy your sodium chloride from your grocer, use Kosher salt, which is not iodized. [Emphasis is mine.]
Notes: Can be used in conjunction with sodium bisulfate to make a substitute for hydrochloric acid."

* If it has use as a restrainer, then it should exhibit some anti-fog properties. Since Anchell states that it is a weak restrainer, I imagine that you would need quite a lot of it. If you tried to add the amount that would theoretically cause it to work as a strong-enough anti-foggant for your purposes, it may not all go into solution, or even be all that economical for you.

** Anchell and/or his editors seem to have an unhealthy aversion to commas, and the bumpy reading it can cause is my biggest complaint about this book.

I would simply mail order the known-to-work and well-documented anti-fogging chemicals. You'll have to wait a week, but you will be better off in the end, IMHO.

Carbonate of soda? That's Na2CO3, not NaCl.

What about Potassium Chloride? I assume its basically going to have as little effect?

Until someone out there shows the use of iodized salt vs non iodized salt, it is not a given that there is any significant antifogging action imparted by NaCl (or KCl for that matter). The error in Anchell should be brought to his attention.

Salt is really more of a weak silver halide solvent than anything else.

PE

2F/2F said:

I do not know if this will help you, but here is the description of sodium chloride from Steven Anchell's "The Darkroom Cookbook, Third Edition:"

Uses: In preparation of chloride emulsions; salting papers before sensitizing and before toning; in hypo alum toning formulas; also acts as a weak restrainer*.

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Anchell is speaking of chloride emulsions when he says that NaCl acts as a weak restrainer. Read the quote again. Chloride emulsions are very slow and are used for contact papers such as Kodak's Azo.

When potassium iodide is used as a restrainer for films a very small amount is used. For example, with the Beutler formula 2.5 ml of a 0.001% solution of KI is added to 250 ml of working developer. Yes, I said 0.001%! I hope this example illustrates just how powerful KI is as a restrainer.

Yes, table salt contains KI but the amount added is probably not measured as accurately as a photographer would want.

To denverdad your experimental results would be creditable if you had chosen a standard developer as the basis of your tests. You also do not state the amount of added salt.

Adding sodium chloride to a developer can increase image sharpness but this has nothing to do with any imagined restraining action. As I stated in a former post the addition of any photographically inert salt can limit developer action to the surface of the emulsion. This will result in greater sharpness but any salt can be added, for example, sodium sulfate would work just as well.

To sum things up, sodium chloride or potassium chloride has no restraining action when used for film. They can only be used for chloride emulsions where their effect a very small effect!

A49 said:

Thank you for sharing your experience. I like the idea to replace the KBr with normal table salt for the fog reducing. If you write 10 ml, then you mean 10 grams, right?

Best,
Andreas

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All my measurements were by volume since I do not currently have a proper gram scale. So it really was 10ml (and actually I think the 5ml was probably enough). If and when I get a scale (I keep meaning to purchase one so maybe this is the incentive I need!) I can figure out the conversion and provide a weight measurement for you.

Photo Engineer said:

Normally, both Table Salt and Sea Salt contain Iodide, and Sea Salt contains Bromide.

Iodide and Bromide are antifoggants especially Iodide even at low levels.

So, unless you used non-Iodized salt, a rarity nowdays in the US, (unless you use Pickling or Kosher Salt) you unwittingly added an extra ingredient that is an antifoggant.

PE

Click to expand...

Actually, I think it was specifically the presence of bromide in sea salt which first made me think to try it. I have to admit that I am a complete hack when it comes to chemistry (physics is another matter). But from things I read online reagarding bromide and fog, I came to a primitave understanding which can be best be summarized by the statement "Bromide = Good" Haha, so I tried the sea salt. Anyway, I was very pleased to find that the more common table salt seems to have a similar effect.

Anon Ymous said:

Denverdad, does the table salt container give any information about the potassium iodide content in ppm?

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I will have a look when I get home. But this was just the ubiquitous Morton's "blue box" variety if I remember right, so you may be able to check for yourself.

Jeff

Gerald C Koch said:

To denverdad your experimental results would be creditable if you had chosen a standard developer as the basis of your tests. You also do not state the amount of added salt.

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Gerald,

Just to be clear, I am not the OP of either this thread or the one referred to by the OP. I have no clue what effect (if any) NaCl wold have on standard developers, nor would I dare to make any claims in that regard. The tests I mentioned were conducted solely for the purpose of improving my results with caffenol-C, and seem to have been successful in that regard.

As an aside, I still get quite a kick out of knowing I can develop film with a "kitchen cabinet" home brew. And for whatever reason, I find that tweaking the caffenol-C recipe to see just how far it can be elevated above a "parlor trick" (to quote you from the other thread), is an enjoyable pasttime. Of course that is not everyone's cup of ...ahem, coffee . But that's fine by me.

Jeff

Edit: Also, the amount of salt added was 10ml for the image shown, as stated in the text and written on the strips in the image.

I dug out my copy of Mason and thought that the following information might be useful.

"Soluble iodides exert a similar restraining action [to bromide], but much lower concentrations must be used. Thus, while potassoim bromide is used over the range of 1 - 15 g/litre of working strength developer, potassium iodide must be used at approximately one thousandth of these concentrations. For similar effects therefore, the two compounds must be used in conentrations very approximately in the ratio of the solubility products of their silver salts.

[Ag+][Br-] = 4.0 x 10-13
[Ag+][I-] = 0.94 x 10-16

By analogy with bromide and iodide, soluble chloride should also exhibit antifogging properties in developers. This is, in fact, the case, but the concentration required to be effective is so high that its use is not practicable. This is because the sollubility product of silver chloride is 1.7 x 10-10. It finds limited practical application in developers for slow chloride papers which do not require much antifoggant action in the developer, the use of even very low quantities of bromide producing too much retardation of development."

L.F.A. Mason, Photographic Processing Chemistry, The Focal Press, London:1966