Hello Brian,
I have etched peweter before with Ferric Chloride. You can get this
at Radio Shack, or any chemical supplier, this also etches copper,
brass, and others. You can mask your design if it is flat, with PNP
transfer paper, just photo copy it onto the paper, and iron it onto
the pewter. If you are not working with sheet you could paint the
object with asphaltum and scratch your design in. You could also use
tape, permanent marker, or paint pen to mask. When you etch make
sure the entire object is submerged, and make sure to agitate the
bath. Pewter etches really fast, check after 5 minutes. Hope this
will maybe help you.
Jill Baker Gower