Personally I use iron III chloride as used for etching circuit boards and, more importantly, as nicked by the every lovely Frau Doktor (thank goodness she has one use) from her Nobel Prize winning employer. Only problem is that the fumes corrode everything in sight and if you get it on your hands you look like the Marlboro man MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.