Jim, Andy,
I have not tried a lot of different types of media. When I find one that seems to work well and not be destructive, I stay with that. A fine grade of glass beads is least invasive. You can get a finish that is smooth enough that there is no need to polish it before bluing.
I like parkerizing, so often I use a coarser grade of flint abrasive to give me a uniform slight matte finish which takes the park well and looks great.
Walnut shells would be great, if they can be ground so that they would feed through a blasting gun. I don't know if such a thing is offered, but I suspect it could not be re-used much before breaking down.
Many years ago I read that in the early 1900s, when they were making the LP08s, the Germans tumbled all those parts in a heated tumbling drum containing moistened ground walnut shells. This also gave the parts their unusual and durable brownish black finish. Mine is just about mint. Does anybody else know about this? I've thought of trying it, just for fun.
That juice in the walnut shells is really powerful stuff, and with the addition of heat and long tumbling time, it seems like something that might work. There are probably also some mild acids in the chemical makeup.
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