To be sure I have left too much oil on the surface of the pan and had to re-clean it from scratch. The pic below shows an example from Nov 2015. It came out of the oven looking a bit like black-and-white film that suffered reticulation during processing. I thought it was Wiped Clean before it went into the oven. This was the second coat. I have had spots before and since but nothing like this.
This is an example of a bad experience with the grapeseed oil from Costco -- which I plan to try again soon. I strongly doubt that their oil was the problem. It was almost certainly something to do with the way I handled the seasoning process.
