[Crex]

If you're just going for a light gray patina etch, why not just use distilled white vinegar with a spot lamp to warm it up? Much cheaper than FeCl or muratic and environmentally safe. Plus it won't damage your skin. It's a little slower but not by much.

Do you plan to use the etchant to produce your logo on your blade or use electronics for that?
You'll get a crisper/clearer logo etch with electronic etching.

Just a note: Put a biscuit of rubber gasket material in the bottom of your class container. If you ever accidentally let a blade slip and drop into the container you will immediately know why it's a good idea.