We had to bake them longer than I thought it would take. After trying 350* for 15 minutes two times and testing temperature in the middle, Anne set the over to 450* for a half hour. That brought about ten pounds of eggshells up to 190* in the middle of the pot.
As for my not understanding the over... It's all digital with all kinds of complicated settings, none of which I understand or care to.
Anne's a violinist and the concert master of the Indianapolis Philharmonic Orchestra. One night she had a concert and left dinner in the oven to stay warm until a buddy and I got home to eat. It took both of us at least 15 minutes to figure out how to turn the #%^^% oven off.