Gary, your variation looks like measurement uncertainty to me. It could arise from variations in sampling technique used in the pot, to which others have alluded, and to instrumental uncertainty at Kester. Any TechNetter ever pull a sample, break it in 2 or slice it down the middle, and have the 2 pieces analyzed for tin? I never did but wish I had. >From talking with Kester, I learned the tin measurement has more uncertainty than those of Cu, Au, etc. I forget the exact numbers, and it was not clear to me Kester itself had a very good idea of what they were. For some years I've been saying the key to success in engineering is understanding the variability (or uncertainty) in the measurement process. Lou Hart -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Gary Camac Sent: Thursday, December 04, 2003 5:14 PM To: [log in to unmask] Subject: Re: [TN] SnPb Solder pot composition I would usually agree with Ed's statement on tin content dropping. I have many years of Kester Solder Analysis Reports, option C, that support that statement. But, for the last four months my tin content has ran 63.16, 63.42, 63.24, and 63.4. No pure tin was added during this period, only virgin solder. Sure has got me scratching my head. Gary Camac --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------