I'm no expert but I believe it's just a matter of consistency. My object is 350 for 15 min. 1 jig or 100, no matter, 350 for 15. Get you a thermometer and check. you'll easily see if a large load alters the temp in the oven. The temp changes when baking food items due to the consistency of the items. Cake, meat, dough, etc absorb the heat. I don't think lead absorbs much. That's just MHO.