Aluminum Bronze
How are fine metal powders/dust ground by hand?
I’ve read that in Japanese lacquer art (maki-e), gold powders that were fine to begin with can be ground even finer by hand. How would they successfully do this, and can this process be used on other metals? (like brass, bronze, copper, aluminum, etc)
Actually, gold is very malleable, so it would be relatively hard to grind. Harder, brittle metals would be easier to smash into powder.
I would suspect that with gold, the metal is first hammered into very thin sheets (gold leaf), and these are then crumpled to produce small flakes. Such thin sheets would be fairly easy to powder. Grinding a metal bar is a messy process, which is fine for something like aluminum, but with gold, you want to make sure you don’t waste any of the metal.
With other metals, the same technique might be successful. Aluminum and copper are fairly malleable. However, other techniques would be able to prepare fine powders more easily and cheaply. Powdered metals are required in large quantities by the paint, pyrotechnics, and rocketry industries I have seen electrolytically prepared copper powder, and other metal powders can be prepared chemically by precipitation or by reduction of a powdered compound of that metal (this is the usual production route for platinum group metals). Something like aluminum is difficult to reduce; most aluminum powder is prepared by spraying the molten metal to produce a fine powder or by grinding down solid bars. This powder may be further refined, for example by ball milling to produce small flakes.
These industrial processes would be difficult to complete on your own, but their use means that these metal powders are widely available for purchase. Expect to pay anywhere from $10 to $30 for a pound of pyrotechnics-grade aluminum powder.
Aluminium Bronze Casting – Sand Castings