Etching with iron(III)chloride hexahydrate

[kai]

How polished should a blade be before you etch it? Does it need a mirror finish?

No polish needed per se - it's a matter of taste or what the traditional approach would be for a given culture/piece.

If you etch a blade that's been cleaned and not polished and no pattern emerges (steel just turns uniformly gray) is it possible that you'd get a pattern if you put a mirror finish on the steel and tried again?

Quite rare but possible: If a blade has been polished with power tools the laminations at the surface may be obscured. If accumulating surface rust has not eaten through this "smear" layer the laminations may still not visible. Repeated etching and polishing (by hand) may help to expose any laminations though.

Regards,
Kai