Barium Chloride

[dogzbum]

Yeah, yeah, I know what you're going to say - it is dreadfully toxic but so is everything else in the darkroom.

Bearing in mind I have no intention to breath, chew or swallow it is there any reason why I should not try Barium Chloride for salt prints?
Anyone want to take a stab at starting concentrations?
Is this stuff even soluble?

 

[Ole]

http://www.hbci.com/~wenonah/hydro/bacl.htm

It's soluble, yes. It's "dreadfully toxic", even more than everything else in the darkroom.

It also forms an insoluble salt with sulfate ("baryte", used among other things for the coating of baryta papers, contrast substance in X-ray examinations, weight material in drilling fluids, filler in paints and other pigments), which makes it somewhat useless in any process involving sulfate, sulfite, thiosulfate and similar anions.

The question shouldn't be "is there any reason why you shouldn't", but rather "is there any conceivable reason why you should"?

 

[Donald Qualls]

Since it's the chloride, not the metal, that makes a salt print work (by forming a silver halide when the silver nitrate is coated onto the salted paper), I don't see where you'd expect to see something different in a salt print made with barium chloride vs. one made with sodium chloride. If you want to make salt prints that are different, try a salt with a different halide (bromide, iodide, maybe even fluoride). My understanding is that you'd generally expect silver fluoride to be very, very slow and require very short UV, but silver iodide has been written up as "insensitive" to light (which seems odd, since I'd expect the weaker bond of a heavier halide to make the compound more sensitive and to longer wavelengths). Bromide is well known to be faster than chloride in applications like gelatin printing papers, however.

 

[Gerald Koch]

silver iodide has been written up as "insensitive" to light (which seems odd

That is certainly odd and wrong. Films like the T-max family depend on silver iodide.

 

[Photo Engineer]

Silver Iodide 'appears' to be insensitive to light due to the fact that it is almost non-developable. So, there may be a great amount of latent image, but you need a very unique developer to reveal that image.

Any halide except iodide or fluoride will probably work, but the barium salts would lead to some severe problems with your effluent. Well, gee, that leaves only chloride and bromide, I guess.

Aluminum halides are not good to use, due to the amphoteric nature of aluminum and its potential to react with gelatin or albumin. Other salts with multiple valence such as iron could work but often interfere with silver halide imaging.

Well, we are back to the alkali metal salts such as sodium and potassium. Now you might want to try ammonium salts, but the ammonia is a silver halide solvent and may mess up the speed of the salt image. It is pH dependant, so if you control the pH the use of ammonium salts should not be a problem.

PE

 

[Gerald Koch]

How can I put this delicately. If you don't have some knowledge of chemistry you should not be experimenting. Stick with established formulas. There are plently to try. I say this so that you do not harm yourself.

 

[Donald Qualls]

Silver Iodide 'appears' to be insensitive to light due to the fact that it is almost non-developable. So, there may be a great amount of latent image, but you need a very unique developer to reveal that image.

Relative to salt prints, though, it's not a question of developing (unless you're doing calotype), but whether the silver can reduce and the iodide can continue to draw silver from the nitrate salt in the sensitizer (a reaction I'd normally expect only if there were sufficient water present, but lots of things act like there's plenty of water in what I think of as dry material). In that environment, I'd think iodide would be (again) faster than bromide. I've heard from another APUG member who comfirms that potassium bromide produces salt prints about two stops faster than sodium chloride, but with reduced range; using an iodide salt seems likely to be further along the spectrum, while fluoride would be at the other end (slower, but with broader range) if one can manage to get it to print out at all.

BTW, where I've read of silver iodide as insenstive was in reference to preparing calotypes -- the paper is pretreated with potassium iodide and then silver nitrate, and exposed to sunlight; this pre-exposure, producing latent image exposure overall, might be part of what makes the calotype so much faster than a common salt print (along with incorporating a developing agent, gallic acid, and then developing out the image with more gallic acid and keeping plenty of excess silver nitrate throughout).

 

[Photo Engineer]

Donald;

To start with, the fluoride salt of silver is too soluable to make a good imaging material and that is why it has not been used. It would be slower than chloride, if it could be used, I suspect, and the sensitivity would be in the UV range of the spectrum.

Silver chloride is the most developable and quite fast, but mainly in the UV region. Silver bromide is faster but in the visible (blue) region, and tends to give lower contrast images. Part of this is due to the excess bromide present in the emulsion. If you take a washed and unwashed emulsion, and compare them (bromide) you see a higher contrast with the washed emulsion in most cases due to the lower amount of excess bromide.

Iodide, up to about 10% is quite useful in many emulsions such as bromide or chloride, but the usual value is from 0.3% - 2% in most cases. Distribution of iodide in the grain is also important.

A pure iodide crystal, as such, cannot be developed by ordinary developers. Too much restraint from the iodide and most developers are too low in activity. But, if you force them, they develop to yield a high speed image with near ortho sensitivity. Pure iodide emulsions are orange red in color and have near ortho sensitivity built right in to them. That is one reason why a pure Br/I emulsion gains speed with added Iodide (among other reasons) is the broadening of the spectral sensitivity imparted by iodide.

Hope this helps.

Gerald;

You have a very good point. Having seen some horrible lab accidents even by trained chemists, you are giving some good advice here. Anyone without chemical training, who does 'research' or 'development' has to assume a very large risk factor for themselves and their families.

PE

 

[dogzbum]

Okay, I get the drift. I shall not bother with the Ba Cl for salt prints.
Gerald, no offence taken, that is why I decided to ask first.

Curiously though my consideration of it's utility was driven by two factors:
1. I read somewhere that K Cl and Na Cl provide different tones in salt prints. True or false? Can anyone prove this?
2. I already have it and don't like to see things go to waste. Perhaps (based on Ole's initial reply) I could use it with some sulphide to provide a superior paper sizing?

Tee Hee... maybe I'll just chuck it over the fence of the nearest hazardous waste facility!! Sounds like the best option.