I noted Dave Hoover's response to the question about d.s. and he suggests resin souyrce as the reason for variability between vendor "A" and "B". I would suggest other possibilities such as treating tension, fabric tension control at the weaver (also lot to lot!), etc. Unfortunately there are probably also phantom variables. Dave, a question. What is the magnitude of the "A" vs "B" vendor difference in d.s. with for example FR-4? Anybody else have any data (or gut feel) regarding the between-vendor variability for the "same" resin system? Chet Guiles Arlon