This is very informative, nice to know there are options that don't include using dangerous acids (I was so worried I'd accidentally spill it somehow and put myself in the ER).
Will this work on a chrome-plated brass sink tube? I'm thinking of etching deep enough to actually let the brass show, which I think would be a very nice look. May make it too thin and weak, but I figure it's worth a try. It looks great in my head, ha ha.