At what temperature (deg F.) does oil begin to form a bond with a cast iron frying pan and why?

For the cast iron skillet, you should coat with oil with about 1/4 inch in the bottom and put it in the oven for 1 1/2 hours at 350 deg. The cast iron expands allowing the oil to into the pores of the iron. Once seasoned, you should never wash in anything but plain water, no soap.