Hi Blair, Unfortunately, your assumption that you know the specific gravity (density) of ED copper is incorrect--you do not know it--it is less than the specific gravity (density) of rolled copper because of organic co-deposits and micro-voids. This uncertainty in specific gravity (density) prevents a direct conversion of oz./ft2 to thickness, and thhat is why ED copper is spec'd in oz./ft2. Regards, Werner Engelmaier Fornercahairman of IPC Copper Fopil Committee --------------------------------------------------- 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 -----------------------------------------------------