Forgive me for repeating myself.... A great test we have used is to put a drop on Silver Nitrate solution (the standard lab reagent 0.1N is fine) on to a Copper surface. A truly clean surface will turn uniformly black IMMEDIATELY. A dirty surface takes longer, and the black coating is less, or non-adherent. There are similar tests for other metals. for Iron surfaces, use a dilute solution of Copper Sulfate and Sulfuric Acid. (CAUTION SELF-PROMOTIONAL STATEMENT!) We use these tests to showcase how well our cleaners work.........:-) Rudy Sedlak RD Chemical Company ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################