The copper sulfate you mention is what would be used for etching brass as well. Process for data plates is to transfer toner to a piece of brass. You can print the text/logo/art and then use an iron to melt the toner from the paper so it moves to the brass. Then when soaking the brass in the charged solution, everything not protected will slowly get eaten away leaving the toner covered areas raised up. You need to mirror any text before printing since you will be laying it onto the metal backwards so what stays on the metal is then read correctly. And it helps to tape the back of the plate so that side doesn't get eaten away. Neat tricks...
I'll have to try your experiment later in the month on a small section of rusty spare track I have. Guess a battery charger would work equally well for power since I've got one with numerous charge rates which can be dialed in.
Wonder if my 3rd grade daughter could use this for her school required science fair project?
