Roger, We validated that microwaving one time will not affect growth promoting properties. We do not reuse agar after it has been remelted and cooled one time. Michael Dr. Michael J. Miller [log in to unmask] http://mypins.com ------------------ The PMFList (http://microbiol.org/PMFList_info.htm) is operated from The Microbiology Network (http://microbiol.org) and supported by our sponsors (http://microbiol.org/sponsor.htm) as a service to the scientific community.