>From all that I have read over the years, I agree; don't use the oven. For the semi-purest. You can buy crystals for HR202 from mhelectronics that are designed for room temp. Although, the consensus is "why spend the extra money"..... Tom Laird WC9M Moline, IL. -----Original Message----- My 3 cents Don't use the ovens period! Les Locklear