Now a bit about safer etching if you are a printmaker.
If you have access to a print studio then see if they offer an Edinburgh Etch bath. You can etch copper and brass with this. I do all my copper etching using this method and it etches well. You can read about the process here:
Some print studios might also offer a Saline Sulfate Etch for zinc, steel and aluminium. This is copper sulfate based. You can read about it here: