Did this about 15 years ago Aluminum etch

Sprayed some black lacquer on some aluminum front and back sides also, and etched my images
Sprayed with wire wheel acid, I believe, or 3M metal prep can’t remember, but an acid wash to remove the instant oxidation the Aluminum gets after it was etched.
Then dropped in a tray of root killer, aka Copper Sulfate and with a spoon of salt.
And watched the aluminum boil away. I made some nice photos on very thin Aluminum also but they all got stolen at a car show. Once etched the black lacquer will wipe right off with some acetone.
Not sure what it is good for but my bird liked his little sign.