Thursday, January 21, 2016

Blogging for Thor: Saline-ent Findings

Sorry for the terrible pun, Spiders, but I'm running out of witty references to salt. This week, it was hard to wait to blog! I was so very excited about the results of my latest experiments. I think this weekend I'll be at the university, making some test prints. I have a hairdryer now! And I'm awaiting the delivery of more chemistry for further testing, too.

Here's what has me all worked up: I successfully printed photograms with non-chloride silver salts. I tested out potassium iodide and Old Workhorse Bromo-Iodizer as catalysts for salt printing, along with a sodium chloride control print and an ammonium chloride side-test. Everything produced a clear, visible image. I'm going to discuss first the basic parameters of the experiment, the controls, and then get into the preparation and results for each halide solution.

Test sheets prior to exposure.
All but one show significant fogging.
Controls: Each of the four prints was made on a sheet of Arches Platine paper, all the same size, all taken from the same full sheet of paper, and all coated at the same time. All four test sheets were first painted with a solution of the chosen halide, then allowed to dry and stored in butcher paper for 3 days while I waited for good printing weather. The night before printing, each paper was given a single coat of 12% silver nitrate, allowed to dry overnight in a dark box. Despite being in a dark box, the drying time was too long. Each test sheet showed discoloration when the box was opened. I will repeat these tests with fresh-dried sheets soon.

Bromo-Iodizer Solution: I used the Bostick & Sullivan Old Workhorse Bromo-Iodizer directly out of the bottle, with no changes to the solution. The solution is easy to coat, and has a strong yellow color that makes it easy to tell where your paper has been coated. It smells strongly of alcohol and should be used only in well-ventilated areas. The bottle should be capped immediately after the solution is extracted.

Potassium Iodide Solution: This chemical comes as a transparent/white crystal solid. I mixed 6 grams of the crystals into 200ml of water to make a 3% solution. I didn't use nearly so much, but I didn't have a small enough mixing container to measure less than 200ml water with accuracy.

Ammonium Chloride SolutionThis is a shiny white powder that does not readily dissolve in water. It required a lot of stirring, and left a film of bubbles and fragments floating in the solution. Again, I mixed the same 6 grams of solid to 200ml of water, resulting in a 3% solution.

Sodium Chloride SolutionFor sodium chloride, the control solution, I used Morton Kosher Salt. As with the other two dry chemicals, I mixed 6 grams of solid to 200ml of water, resulting in a 3% solution. This is a medium-strength salt solution by standard salt printing guidelines.

The prints were made in windows at my apartment, on a clear, sunny day. I exposed all four prints for 2 hours before pulling them and scanning the resulting images. None of them have been fixed, though I may do a potassium iodide fixing test just to see what happens.

Bromo-Iodizer Print: Unlike any other salt print I've seen, this one came out blueish-green, but mottled with little flecks of a more yellowish green. I was told to expect some issues due to the high alcohol content of the bromo-iodizer, but the green color was totally unexpected.
Potassium Iodide Print: This print is much paler than a normal salt print, more of a tan than a brown. It's still fully detailed, just lighter. I really want to see this printed again without the fogging, so I know what it looks like in a "proper" exposure.
Ammonium Chloride Print: Very similar to sodium chloride, though the pre-exposure fogging makes it difficult to read nuances of hue and tone. I'll have to do more specific experiments regarding the different forms of chlorides to see the exact effects of ammonium vs sodium. If there is a visible difference, it's that the ammonium chloride has a cooler, more purple tone to the browns.
Sodium Chloride Print: Exactly as expected, though unfortunately tainted by the long wait between silver coating and printing. Silver chloride, if left in contact with organic matter (like the paper), will self-expose even in darkness. That results in the violet-brown staining of the paper, and the extreme violet outlines around the image.

So, my final thoughts? I'm very excited to have proven to myself that silver chloride is not the only halide that can be used in salt printing. The potassium iodide image is considerably blander than I had hoped for, but the strange jade color of the bromo-iodizer image gives me hope for future tests. I still haven't tested potassium bromide by itself, or tested non-potassium forms of bromide and iodide. I know from previous experience that potassium chloride isn't the best form of chloride to use, so maybe potassium bromide and potassium iodide aren't the best forms of those halides, either. I'm going to look into obtaining other solutions of bromide and iodide, maybe even some alternate forms of chloride. The ammonium chloride is similar enough to sodium chloride, but I've yet to test pure potassium chloride to see the result. I've only ever used it in a "lite salt" mixture: 50% sodium chloride and 50% potassium chloride.

There's just so much more to do, Spiders!

Thursday, January 14, 2016

Blogging for Thor: What's in a Halide?

The three common silver halide precipitates:
AgI, AgBr & AgCl (left to right)
Hey there spiders! I'm gunna hit you with some SCIENCE!

Modern silver gelatin photography uses the term "silver halide" a lot. In film and in paper, the term gets tossed around in reference to the light sensitive salt used to make photographic images. "Halide" is not a specific chemical, though. There's no such element as "Haline" on the periodic table. Instead, "halide" refers to a group of chemicals: chlorine, bromine, iodine, fluorine, and astatine. So a silver halide is a silver compound with any of those five elements. Two of the silver halides are weird, so I want to go into detail on them!

First off, silver astatide isn't used in photography because astatine is extremely radioactive and compounds using it decay in a very short time. So, while silver astatide does exist, it isn't physically feasible to use for any practical purpose. The short half-life of astatine means that it's difficult to study even in laboratory situations, so the light sensitivity of silver astatide isn't even well documented.

The other weird silver halide is silver fluoride. It exists, it isn't radioactive, but it still isn't used in photography... for the most part. Silver fluoride exists in three forms: disilver monofluoride, silver monofluoride, and silver difluoride. None of these forms of silver fluoride are useful in traditional photography, primarily because they react with water. Depending on the specific fluoride compound, they will either oxidize violently or break down via hydrolysis. Because of the inability to use silver fluorides in combination with water-based chemistry, silver fluoride was long ignored in photography. However, in 1966 a US patent was filed for a process where silver fluoride could be vacuum deposited onto a surface along with gold, and treated with boron trifluoride vapors to create a high-resolution, extremely low-speed photographic surface. It appears, though I'm not an expert at deciphering patents, that this research was carried out in connection with the Polaroid Corporation, by a scientist named Joel M. Peisach. I've had no luck tracking down any further literature or contact information regarding this process, and certainly no examples. It's extremely disappointing, even if the complex process and materials required put this technique far outside the reach of anyone working outside a laboratory environment. Still, it was really, really cool to find out that silver fluoride photography does exist.

Silver chloride, silver iodide and silver bromide are all widely used in different forms of photography. Each compound produces different tonal ranges, color palettes and contrast ranges and functions in different photographic processes. Generally, silver chloride is the form used in salt printing.

Why the big science dump, Spiders? Because I'm all about breaking the rules and getting into the how and why of things. So, who's to tell me that a salt print uses silver chloride? Why can't it use silver bromide? Or silver iodide? Or a combination of two halides? Or all three halides? Why can't it be as halide happy as it can get, Spiders? It's about to get like that, Spiders. I'm searching for ways to make "salted paper" images using silver bromide and silver iodide in addition to, or in place of, silver chloride.

Fortunately, I found this weird stuff called "Old Workhorse Bromo-Iodizer" in my university's alt process lab, and I found Potassium Bromide for sale from Bostick & Sullivan. I need an iodide solution, but I'm sure I can find it. After all, iodine isn't exactly hard to get a hold of. This is going to get crazy, Spiders.