Could anyone tell me why when I have seasoned a couple of my cast iron skillets it did not season evenly? There are some spots that seasoned well and some that looks like it did not. I have done other pans and have not had this problem but they were not as smooth as these pans. This last one that I have seasoned Last night and did it for the second time this morning I did at 400 degrees for 1 1/2 hours upside down in oven. Did another one at same time and it did fine. Does anybody have any suggestions? Would greatly appriciate it. Thank you, Bev