Homebrew PCBs

I'm a bit curious.  I've read online about Photo Etch setups, and one 
thing that seems popular is an acid solution that grows as you use 
it, basically it uses chemicals that will combine with the copper to 
create more acid each time you etch.

What I'm curious is if there is a similiar etching solution that 
could be used for Brass?  Since I'm interested in photo etching from 
a modellers perspective, I'd rather use cheaper brass. :-)

TIA
-Gary