I don't know if this will be of any help with regard to
achieving a matt finish but I thought it might be worth passing
Years ago I was discussing "sand blasting" of metals ( not
jewelry ) with a tool and die maker. He suggested using ordinary
"granulated sugar" as a blasting media, as apposed to sand or
He claimed it would produce a very fine "satin" texture.
I haven't tried this but would love to know the results, should
someone be willing to experiment.
My suggestion would be to try this on material that you are
going to melt for casting rather than a piece that you have
produced, in the event it doesn't provide the desired results.
If one or more of you try this......please let all of us know
your results. We're all here to learn. Best of luck.
Very best regards