Peter: The tarnish you are seeing is easily removed by any acid cleaner that contains thiourea (and not Hydrochloric Acid). Most of the chemical vendors serving the pcb fabrications industry have such a product. I mention not using Hydrochloric Acid, because the solder deoxidizers which used to be used after ammoniacal etching were a combine of Hydrochloric Acid and thiourea. Rudy Sedlak RD Chemical Company --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------