On Aug 31, 6:56 am, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley
8.3.70:

Running the redox again, FeCl3
could dissolve some iron to yeild FeCl2, but it would be darned slow...

Yep. I've etched stainless with FeCl3, it took half an hour to go 5
mils.
Turned a sheet of shim stock into custom-size washers that way.

Marking, though, doesn't need much penetration. I've also
(accidentally)
got a little oxalic acid (used for bleaching wood) on a stainless
knife,
and it left quite a mark, frosting the surface (which started
polished).

Which is best, I wonder: polish the blade, then etch to make a frosty
mark, or etch, blue the blade, and polish to make a contrasty mark?