Tom Gootee's article is worth reading. He did a lot of the heavy lifting summarized in this article. I've tried this and it works -- but... You must be very,

Tom Gootee's article is worth reading. He did a lot of the heavy lifting summarized in this article. I've tried this and it works -- but... You must be very, very careful with the solution -- whether it's Ferric Chloride from Radio Shack or a muriatic/peroxide homebrew. Gootee's article and others show how to create safe 'bubblers' for this step. Look at these first. Please be careful. You are entering 'Breaking Bad' territory here.