I'm part of the kitchen crew for a 300 person weekend retreat. Friday Lunch includes a baked potato bar, so we wash and poke holes in the russet potatoes Thursday evening, lay them out on sheet pans and bake them Friday morning. They sit out on the sheet pans in bakers racks overnight in the kitchen. Last year, we had a large number of potatoes that had nasty bluish black spots inside when we cut them open for service. Anyone have any ideas why that happened? Should we not have pierced them until just before being placed in the ovens? Or were they badly bruised and we didn't know it until after they were baked and split open? I'd like to know what to do before this years retreat.