I must have been sleeping during the whole No-Clean introduction. I thought they were based on similar chemistries as Rosin, but with lower solids. A quick web search shows some are rosin, but most are "synthetic resin". The Resin definition says it is a derivative of Rosin. The MSDS of some say "Petroleum Distillates." So, can somebody explain what chemistry is in a No-Clean flux? What does "synthetic" actually mean? Thanks, Glenn --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 -----------------------------------------------------