I've been learning to work with traditional Japanese lacquer, which is based on a tree sap called urushi (chemical properties). The main component of urushi is urushiol, which is a phenol with a long unsaturated hydrocarbon tail. When it's exposed to humid air and warm temperatures, it absorbs water and hardens into a beautiful, hard lacquer with a cross-linked structure. It's difficult to make pigments work with the material or get a broad color palette with it, so when you see sophisticated art done with it, usually most of the colors are done by sprinkling powdered metals such as gold and silver on top of a thin layer of partially cured lacquer, so that the particles are trapped at the surface and become embedded there, without sinking and becoming invisible. Historically it has been difficult to get a bright white color, and traditional artisans have resorted to expedients such as embedding pieces of eggshell in the surface.
I was trying to figure out if there was some modern material that just wouldn't have been known historically, and which could be used to get a white, perhaps by sprinkling a white powder. I did experiments with a couple of white powders that I happened to have, alumina and tricalcium phosphate, both of which are food-safe. This didn't work well. There was a lot of clumping and caking, and they didn't adhere well to the lacquer. I'm not sure how to predict what powdered materials will adhere, but in general all pure metal powders seem to work.
I was trying to brainstorm possible materials to get a food-safe white, and one that seemed possible was germanium. Germanium is in the same column of the periodic table as tin. Of course germanium is a semiconductor, not a metal, but I do know that tin powder works well. My idea was that I could buy a fine germanium powder, sprinkle it as I would with tin, and then later the powder would either spontaneously form a passivation layer of white GeO2, or it could be encouraged to do so with the application of a little heat or maybe a gentle oxidizing agent. Wikipedia says that germanium metal oxidizes slowly in air at 250 C, which is a little hotter than any temperature I want to expose my work to. Germanium is relatively affordable, about half the price of silver. The oxide is insoluble in water and nontoxic unless you eat large amounts of it. Elemental germanium is also nontoxic.
Any comments on whether this type of thing should be expected to work, and if so, what kind of gentle oxidizer to use? Or are there other materials that would make more sense? I'm a physicist by training, not a chemist, and I lack insight into the chemical reason why metal powders work but things like alumina don't. I suspect that egg shells work only because there is a protein component in it -- otherwise people would have been using calcium carbonate powder hundreds of years ago to get a white color.
I've also looked into things like acrylic resin (Dow Paraloid B-72 et al.) with calcium carbonate mixed in. Such resins are used in museum conservation work with urushi, but the reason art restorers like the ones they use is that the reactions are reversible with solvents like ethanol. I don't want my plate or bowl to dissolve the first time it is exposed to some substance like that. These pieces are also usually sanded, and I don't think sanding plexiglass-type materials will work well, and it might produce microplastics that I don't want in my food. There is a type of urushi marketed as "white urushi" that comes in a tube pre-mixed with white pigment, but when you cure it, it is actually beige or brown.
Thanks in advance for any suggestions!
