I still wish I could find a book/document/etc that describes the building o= f a vacuum system for the range of 1 torr to 10 microns or so. Seems to be a black art. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .