Jon Hilty
Some notes on various mercury alternatives
Although excellent results can be achieved without any sort of reflector, the idea of finding a true replacement for the mercury used in the original process has always been alluring. This has been a surprisingly difficult problem to figure out due to a variety of different reasons that will be detailed following this. Sometimes I find myself tunnel-visioned on solutions that require such outlandish equipment or procedures, that every once in a while I have to pause and ask myself, "wait, wouldn't mercury be easier at this point?".
I've tried a bunch of random stuff over the years to varying degrees of success, and I figured I might as well centralize what I've found, since previously my results existed scattered across rambling instagram descriptions.
Galinstan
Galinstan is a extreme low melting point alloy of gallium, indium, and stannum (tin). It us unfortunately one of the most obvious solutions, as it looks nice and shiny like mercury, and stays liquid as long as the temperature is above -19C, which tends to be the case for my house. The unfortunate reality is that unlike mercury, whose oxides form somewhat slowly, gallium forms its oxides pretty much instantaneously. And the more unfortunater part is that gallium oxide loves to stick to pretty much anything and everything. Every time I decide I'm going to try this again, it creates a messy nightmare to clean up.
In 2018 I made this video detailing some of the problems I ran into in some early attempts, however, I regretted never actually shooting any plates with it. So this year I went ahead and actually did that.
I designed a holder that was just about as leak-proof as the last time I tried to design one, but it held enough against the plate to at least prove out whether it was worth pursuing or not. An exposure was made, and then then excess galinstan was removed with a cotton ball and some water.
Results were not great - there was heavy fog all across the plate, the lowest of which was in the center, where the galinstan would have made initial contact. Possibly this is the area where the least gallium oxide had contacted the emulsion - I'm not really sure. The red flowers are indeed visible, so it does seem to have worked to some extent. I tried rubbing the plate with a cotton ball and some soap after development to see if the fog was just some sort of surface deposit, but it seems to be occurring within the gelatin as well.
I noticed that when the galinstan had wetted the plate, the portions of galinstan that clung on stubbornly seemed to produce a very good mirror effect, and the plate could be moved/rotated without it dripping off. A second plate was prepared, this time by just pouring some on and spreading it around, and then allowing the excess to drain. The coverage was not complete, however, I felt this would make a good control.
The plate seemed to experience heavy fog, even in areas where there was no extended contact with the plate. The fog was so heavy that parts of the plate, which typically appear red when viewed via transmission, are blue for some reason. I'm not sure if trace metal oxides are dissolving into the developer and causing fog, or if its some sort of other mechanism. The only thing I can think to try before giving up forever, is to remove the galinstan in a weak solution of HCl before development.
Gallium
Back in 2019 I tried out gallium - I figured that I might be able to "cast" a solid mirror against the plate, and melt it back off later on. This actually worked out a lot better than I had thought it would - it usually would solidify as a fairly clean mirror (occasionally with a fractal, crystal-like pattern). And there was no need to "melt" it off, as it would pop off in one piece fairly easily (at worst, requiring some gentle prying with a small screwdriver). I didn't have much of a concern that the heat would cause fog or grain growth, as gallium melts at a mere 30C.
I don't really recall the specifics, but the sandwich could be loaded into my Bronica and exposed/developed as normal. The plate exhibited heavy fog, even around the edges where the gallium never would have made direct contact. The solid gallium seemed to leave a faint "residue" on the emulsion after removal (anyone who has touched gallium will know what I'm talking about). The residue was not removed before development.
Colors were very strong, and possibly were "correct", as back when I would have been using a lot of red/orange sensitizers to combat the somewhat weak reds that are produced from air-gelatin plates. The fog does appear to "drift" a bit into uncontacted areas, lending more credence to the idea that dissolved gallium oxide in the developer may be the cause of the fog.
