sharpening files with acid

I read a very old carpentry book once, that described a way to
sharpening files with sandblasting,
something with sandblasting against the back of the teeth to remove the
worn part of the teeth.
I would think you are doing something similar with the acid. fredb

BOGGS TOOL & FILE SHARPENING COMPANY
http://www.boggstool.com/
No connection to seller blah,blah,blah.

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> Somebody told me about this and I tried it. It does a lot better for
> dull files than I would
> imagine Rogaine does for hair. I took an old flower vase and filled it
> with muriatic acid.
> I placed all my old rasps and files in there and waited about four
> days. I washed the acid
> off the files with an old can of generic soda pop and they are
> noticeably sharper (not just
> cleaner) but not quite as sharp as brand new.
>