Some chemical questions about salt printing

Hey everyone--

Playing around with salt printing to get my feet wet with alt processes. Having lots of fun so far, and planning on graduating to kallitypes once I'm comfortable and getting good results with salted paper.

I've been playing around with chemistry, paper, sizing, single vs double coats of silver nitrate, etc. etc. There are so many variables in alt processing, more than I'm used to after years of silver gelatin printing. So I have a gaggle of questions. The most important one right now is question #1. The rest are in no particular order. Hoping to get some wisdom from the veteran alt process folks here.

1. I am trying two different salt coatings right now. The first is the Bostick & Sullivan salted paper kit. The bottle it came in is labeled simply "salted paper sensitizer." I don't know if it's NaCl, NO4Cl, what the dilution is, whether it contains any sizing agents, etc. The second is a homemade one, which is 2% NaCl with 3% gelatin as a sizing agent mixed in distilled water. While my own NaCl + Gelatin stuff does seem to work fine, in side-by-side tests against the Bostick & Sullivan stuff, mine fogs much more readily (even under safelights), and doesn't seem to yield quite as dark of a dmax given the same exposure and processing. Does anyone know what is in B&S's salt mixture? I've heard of sodium citrate, potassium citrate, etc. being mixed in with the salt, but don't really understand what the addition of those chemicals accomplishes, or how much to add, etc.
2. What is the best way to improve my dmax? I see this as the biggest weakness of salted paper prints - the somewhat underwhelming dmax makes the tonal scale feel much less impressive.
3. What can I do to achieve a sharper image? I'm working with negatives I know for sure are sharp. 3% gelatin in my salt solution doesn't seem to make any difference in print sharpness, despite being a high enough concentration that it's more gelatinous than liquid at room temperature.

Happy to hear from anyone more knowledgeable than myself here. If there's any information I didn't volunteer that would be helpful, let me know.

BHuij said:

NO4Cl

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That's not a theoretically possible salt. Both Cl and NO4 are anions. Perhaps you meant NH4Cl (ammonium chloride). It's unlikely B&S would resort to the use of this salt, which tends to fog prints much more easily, than the omnipresent and known-to-work Na4Cl (which coincidentally is cheaper as well).

BHuij said:

Does anyone know what is in B&S's salt mixture?

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No, but it's conceivable that there is a tiny amount of citric acid present in it. I don't know.
Have you tried your own salt mixture without the gelatin? There can be impurities in the gelatin that create fog. The same with salt; table salt can contain iodine salts (it should be sold as iodized salt in this case) which will fog your prints. Make sure to get table salt that's as pure as possible. Usually this is the cheapest kind that cakes/lumps easily as it has no anti-caking agents added to it (these may also interfere with printing).

BHuij said:

I've heard of sodium citrate, potassium citrate, etc. being mixed in with the salt, but don't really understand what the addition of those chemicals accomplishes, or how much to add, etc.

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As I recall they're mostly used to slightly enhance dmax and/or subtly alter image tone. I didn't find the addition of citrates necessary at all, or clearly beneficial when I tested it some years ago. For me, the best approach is still the simple, tried and tested salting solution of only NaCl (the cheapest table salt I could find), and a silver solution of just silver nitrate and some citric acid. The latter is a very effective anti-fogging agent.

BHuij said:

What is the best way to improve my dmax?

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1: Use a suitable paper. Only a few papers give optimal results. I can't tell you which ones; paper availability is too variable across the world. Papers that work well for me are probably unobtainium for you.
2: Try the citric acid added to the silver nitrate solution if you haven't already.
3: Use a suitable negative and sufficiently long exposure time. Actually this should have been at the top of the list. 99.5% of the salted paper prints I see being posted by people are of poor quality (IMO) because of this problem. They use negatives, often inkjet printed, with an insufficiently long tonal scale / insufficient density. It's IMPOSSIBLE to make a decent salt print from a poor negative. You either end up with a print with good dmax but too dark highlights, or good highlights and poor dmax.
4: Gold toning can enhance dmax. But don't bother yet if you don't get a decent dmax without any toning first.

BHuij said:

What can I do to achieve a sharper image?

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1: Use a paper that's hot-pressed or otherwise 'doctored' (e.g. using additional sizing) to have a very smooth surface. The coarser the paper surface, the more fuzzy the print. I prefer reasonably smooth paper surfaces, and no additional sizing (see final comments in this post).
2: Ensure absolutely perfect contact between the negative and the paper during exposure. A good, solid contact printing frame is important. Of course also make sure you've got your negative with the proper side pressed against the paper; emulsion-to-emulsion.
3: Use a collimated or point light source instead of a diffuse light source. UV tubes, led strips etc. are diffuse sources and as such are far less forgiving for less-than-optimal negative-to-print contact. Sources like metal-halide bulbs, a single high-poer COB led at large distance from the print (e.g. 2ft or more) and of course the sun are (practically) point sources.

BHuij said:

3% gelatin in my salt solution doesn't seem to make any difference in print sharpness

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Indeed, I noticed this as well. If you want sizing to make any meaningful difference, try sizing your paper twice or so with a 10% gelatin solution. It's way heavier than what you're doing and will likely result in challenges getting an even coating with the salt/silver emulsion, but the paper starts to move a bit towards a glossy silver gelatin kind of paper. You could of course also try to sensitize fixed out enlarging paper, but I never tried this. In any case, a hot-pressed paper without any additional sizing can produce pretty sharp salt prints. Hence, I never bother with additional sizing etc.

1. Maybe the kit version is somehow contaminated. The "fogging" might be chemical reaction to something?

2. Make high dynamic range negatives. I haven't treid myself but gold chloride toning should increase the dMax and keep the print more black. I personally like the orange/brown tone and pick the motif that suits this printing technique.

3. I believe only thing that can increase sharpness is the paper you are using? I'm not sure, not an expert

I haven't used gelatin as base but maybe I should. Also albumen prints would nice to try, I have had albumen ripening from last winter, I think it is done ..

edit: Koraks was faster .. and more detailed

I think that @koraks thorough reply covers everything well, but here are a few additional thoughts.

As for using citrate with the silver nitrate, from what I read in Anderson's salted-paper book, adding the citrate to your silver nitrate stock can be problematic (precipitates forming on storage, if I remember correctly). I get around this by using two stock solutions 12% citric acid and 30% silver nitrate which I mix in a 1:1 ratio immediately before applying it to the paper.

As for the salt, it is imperative to use pure NaCl. If you are not buying lab grade material check the ingredients on the package carefully. I use Diamond Crystal Kosher Salt from the grocery store routinely. Every other brand of Kosher or pickling salt I have found has additives.

As for image sharpness, I'll reiterate the need for good even pressure in your printing frame. You can try adding a sheet or two of heavy paper cut to the full dimensions of your frame to slightly increase the pressure.

I'll end by stressing the need for a proper negative. If you are using digital negatives, getting the curve used to prepare the negative is critical as is using an ink which gives adequate density in the UV.

Kind of weird B&S calls the salt solution "sensitizer." Have you tried calling them? They might tell you what's in it or ask for a MSDS which might list the ingredients. You won't get the exact recipe so if your goal is to mimic their solution, you might end up spending too much time experimenting. You will probably be better off starting simple as suggested above and make it more complicated (with sizing, alternative salts, citric acid, citrates etc) as need arises.

Did your kit also contain some potassium dichromate? If so, you can use that to increase the contrast - allowing you to increase the exposure to get better Dmax without fogging up the highlights (so they say, never used it myself.)

Regarding toning, you might find this thread interesting:

https://www.photrio.com/forum/threa...out-black-salt-makes-a-terrific-toner.148338/

In this particular case, toning with Himalayan black salt gave me a boost in Dmax as well as contrast by bleaching the highlight densities. These are not dramatic improvements so as Koraks suggests, get the best Dmax to start with. In this case at least it costs next to nothing compared to gold and easy to procure.

:Niranjan.

Great info everyone, thank you. I’m aware of the need for curve building with my transparency negatives and have started that process.

Since the gelatin isn’t doing me any good, I think I’ll just omit it and try 2% NaCl. The salt I’m using is Kroger brand kosher salt. I don’t believe it has additives, but I’ll check.

I’m aware that trying to store AgNO3 with additives can result in precipitates spoiling the sensitizing solution, but is there any harm in mixing some citric acid in with the salt solution? Or am I better off mixing it in with the silver nitrate in the shot glass immediately before applying to the paper?

I’m trying to avoid using the potassium dichromate. Stuff scares me.

nmp said:

Kind of weird B&S calls the salt solution "sensitizer."

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Agree, and I thought maybe OP had made a mistake when he wrote that. But at the B&S site, they also call it that.

My hunch, like Koraks also guessed, is that they add a bit of CA to the salt solution. I've used 0.5% CA in salting solution occasionally. To make and sell a kit with straight AgNO3 actual sensitizer, maybe they add a bit more than that. They'd probably tell you if you emailed and asked!

( OP and I were typing at the same time ) Edit: #1 thing, as Koraks said, is to try different papers and find a good one. Your kosher salt might have a tiny amount of potassium ferrocyanide anti-caking agent, but not enough to make any difference. Differences in salts, I think, are more due to source of salt ( which mine, salt lake, sea evaporation pond, etc etc...).

fgorga said:

As for using citrate with the silver nitrate, from what I read in Anderson's salted-paper book, adding the citrate to your silver nitrate stock can be problematic (precipitates forming on storage, if I remember correctly).

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Yeah, good point; as said, my experience with citrate is really limited, but as a rule, I would always store the silver nitrate as a pure solution with nothing added to it. It keeps forever that way - plus, it can be used for different purposes! I found an 11% silver nitrate silution to be a very flexible tool in the box; it works not just for salted paper prints, but also for various other purposes.

NedL said:

Agree, and I thought maybe OP had made a mistake when he wrote that. But at the B&S site, they also call it that.

My hunch, like Koraks also guessed, is that they add a bit of CA to the salt solution. I've used 0.5% CA in salting solution occasionally. To make and sell a kit with straight AgNO3 actual sensitizer, maybe they add a bit more than that. They'd probably tell you if you emailed and asked!

( OP and I were typing at the same time ) Edit: #1 thing, as Koraks said, is to try different papers and find a good one. Your kosher salt might have a tiny amount of potassium ferrocyanide anti-caking agent, but not enough to make any difference. Differences in salts, I think, are more due to source of salt ( which mine, salt lake, sea evaporation pond, etc etc...).

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Yeah, it's weird and I guess technically incorrect the way B&S has labeled their bottles. Kit came with 2 bottles (not including the potassium dichromate). One is salt solution of some sort, and labeled "salt print sensitizer" despite not actually being a sensitizer. The other is just labeled Silver Nitrate 12%. AFAIK it's straight AgNO3 with no other additives.

Thanks again to everyone for useful feedback. I have on order from B&H some Hahnemuhle platinum rag and some Pictorico transparency film. I think that will probably be the best "next step" for me to get a really solid result from this process. I've been using Strathmore hot press watercolor paper that I could find locally here and Fixxons film. The Strathmore stuff seems like a nice paper, just maybe not the right fit for alt processes. In any case, all my research has said to just bite the bullet and shell out the little bit of extra money for the HPR, Arches Platine, or Bergger COT 320. If for some reason I really end up hating the HPR, I'll try the other two and see what works best for me. The Pictorico film should help too. Near as I can tell, even my "pure black" 100% ink density on the Fixxons film isn't giving me a paper base white at the exposure time it takes to reach dmax under my UV lights, so again I'm hopeful that upgrading my negative material will let me get a longer tonal scale.

I think I'm going to put in an order at the formulary for kallitype chemistry tonight. If I decide to revisit salt printing in the future, I'll need to remember to forego the gelatin sizing in my salt solution and try adding about 0.5% of citric acid to help hold back the fogging. With the B&S "sensitizer" that we're assuming is just NaCl and probably citric acid, when I stick with a single coat of silver nitrate, fogging is a nonissue. The double coat of silver nitrate yields only a barely perceptible increase in dmax, so I think I'll stick with a single coat in the future.

Once again, this community has come through with a wealth of experience and knowledge. Thanks again for everyone helping out the noob.

BHuij said:

Near as I can tell, even my "pure black" 100% ink density on the Fixxons film isn't giving me a paper base white at the exposure time it takes to reach dmax under my UV lights, so again I'm hopeful that upgrading my negative material will let me get a longer tonal scale.

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I'll say a prayer for you.
Not to discourage you, but my own foray into the digital negatives realm was by and large a frustrating disappointment. Inkjet printers are wayward to begin with, with their constant cleaning of heads, pizza wheel marks (Epson 3880 here), nozzle alignment issues (not a problem for regular prints, but gets important if anything about 600dpi actually matters!) etc. etc. Add to this the problem you noted regarding density, and oh, forgot to mention: the fundamental (physical & chemical) mismatch between a polymer transparency material (i.e. the film) and a water-based pigment dispersion (the ink). I've seen all manners of smears, dotted patterns, mud crack patterns etc. - but no actually sufficiently solid blacks to achieve good light blocking. Yes, I tried several transparency materials, ink densities, ink colors etc. I did NOT try Pictorico OHP as it was virtually impossible to get here in Europe back when I messed around with this approach.
I made hundreds if not thousands of prints; cyanotypes, Van Dyke Browns, carbon transfers, salted paper, not to mention quite a few photopolymer intaglio prints. In the end, my conclusion was that at least my printer (again, Epson 3880) was not up to the task of delivering the necessary resolution (without ugly digital dithering artifacts) combined with the necessary blocking power for processes like salted paper or even Van Dyke Brown (classic cyanotype was totally fine of course). Hence, I decided that to make digital negatives work, I would have to:
* Shell out the cash for a new printer with an even better head
* Shell out the cash for a conversion set from regular CMYK to something like Jon Cone's piezography set for better gradation (using only e.g. black and yellow gives *very* ugly tonal transitions / posterization / dithering no matter how you tweak the printer's nipples).
* Revisit the whole transparency film testing thing again, possibly having to resort to starting from scratch with a suitable substrate, subbing it myself etc.
In short, I decided that digital negatives can certainly work - but to get them to work WELL takes a similar kind of investment as assembling a (ultra) large format camera kit at the desired size and using that.

So instead I just used the 4x5" and occasionally 8x10" cameras I had on hand anyway, slid in a sheet of €0.50 fomapan, developed it and had a PERFECTLY FINE negative to print with.

It took me many months of fiddling with the supposedly accessible technology of digital negatives only to realize how cheerfully simple in use a piece of large format film is...

PS: don't get me wrong; even with the printer you have on hand you can make digital negatives that produce OK-ish prints. It might be fine for your purposes. Just don't expect full access to the long tonal range of a salt print (at least not easily) - and don't take a magnifying glass to the print if you don't like seeing little dots all over the place. A printer in the end will always be a pixel machine and it DOES show in the print. Inkjet is designed to have a certain ink bleed, and OHP film does not bleed (if it does, it's bad news and creates problems all of itself) so the tiny dots make it all the way to the final print.

Yeah, it didn’t take long when I was first starting to read about these alt processes to realize that making negatives with an inkjet printer is its own entire rabbit hole. Luckily I have access to a P800. My dad and I share the photography hobby, and he bought the printer for making photo prints.

That said, if I can’t get satisfactory results with the Pictorico OHP, some work to build the right curve, and a better paper using the kallitype process, I will just go analog for making negs intended for salt or kallitype. The appeal of inkjet negs is that first, I can keep shooting my film cameras and using the calibrated zone system development I worked up for silver gelatin printing, and second, that I can print photos from my non-analog camera using an analog process. A 4x5 sheet developed for kallitype or salt printing will be basically impossible to use for silver gelatin.

Then again, maybe this will be what finally convinces me to get an 8x10 camera…

@koraks That is what I have understood also. However few weeks ago on gum print workshop all of the participants had digital negatives except me (I had 5x7" film negatives) and they got nice prints made. I couldn't see any digital negative problems there. Many didn't have any "fancy" printers either to print with. That confused me a bit..

Regarding digital negatives...

There is, no doubt, a learning curve to climb when starting down the digital negatives path. However, that hill is no where near as steep as learning to process film in the darkroom.

Beginners often have the wrong idea about digital printing (of negatives or positives)... digital printing is not a 'just push the button' process. To print well in either realm (digital or analog) requires skill and patience. The right tools also help.

The key to printing digital negatives is the curve one applies to adapt the contrast to the negative to the print process. Making curves from scratch is a long, technical iterative process. There are many systems out there that purport to automate some of the process. (I have never used one, so I can't make a recommendation.)

That said, my standard advice to beginner digital negative printers is don't reinvent the wheel... instead, beg, borrow or steal a curve from a more advanced practitioner.

Where to get curves? They are out there on the web, just search. Some books on alt processes contain curves. (Anderson's cyanotype book has them.) One can also ask folks to share their curves; most are happy to do so.

After you gain some experience with the entire process then you can, if you need to, learn to make a curve from scratch or to modify the curve you are already using to fine tune your output.

What sold me on digital negatives is their flexibility.

Here is an example of a cyanotype made with a digital negative... I think that it is a nice print.



More examples (both cyanotypes and salted-paper prints, all made with digital negatives) can be found here: http://gorga.org/blog/?page_id=5358. Digital negatives can work just fine for cyanotype!

OP
if you tone in the Himalayan salt make sure you fix completely before you do that, putting your print in the salt again may reinvigorate / retrigger the silver .. that was Talbot's problem when he used salt as his fixer before Hershel told him about hypo... have fun with the digital negative if you go that route. I have used a low-end epson all in one 640 expression to make all my digital negatives and they came out very nice, as nice as my classmates who were using the school's giant (expensive! ) printers and at least as good as classmates who were using film.

Koraks, do you have any bulb recommendations?

koraks said:

I'll say a prayer for you.
....

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Koraks, I've been meaning to come back to this thread to say "thanks" for taking the time to write that out. Your perspective and experience is interesting. I haven't gone down the digital negative rabbit hole myself, so have nothing to contribute. I would also like to mention that paper negatives can work nicely for a number of printing processes, although they have a learning curve too.

FYI just to close the loop here, I should say I ended up finding a curve that gave me good results. I'm now coating with a DIY puddle pusher, using the B&S salt solution and silver nitrate, and I think I got the density I need using the stock Epson drivers with OEM photo black ink in a P800 on Fixxons transparency film. I built out a curve as best as I could in Photoshop, and printed an 8x10 negative of a white flower against an effectively pure black background. The final salt print came out with a surprisingly good dmax, and well-preserved highlights that closely matched paper base white.

I think there is more salt printing in my future, but for the time being, I'm wrestling with kallitypes. Thanks all for the help.

BHuij said:

FYI just to close the loop here, I should say I ended up finding a curve that gave me good results. I'm now coating with a DIY puddle pusher, using the B&S salt solution and silver nitrate, and I think I got the density I need using the stock Epson drivers with OEM photo black ink in a P800 on Fixxons transparency film. I built out a curve as best as I could in Photoshop, and printed an 8x10 negative of a white flower against an effectively pure black background. The final salt print came out with a surprisingly good dmax, and well-preserved highlights that closely matched paper base white.

I think there is more salt printing in my future, but for the time being, I'm wrestling with kallitypes. Thanks all for the help.

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It is far more believable if we see a picture or two.....