There is yet one more detail I seem to have just understood about cooking in cast iron pans.
After use (frying onions, frying potatoes, ..) the pan must be cleaned quite soon, perhaps within 24 hours of use.
This is the case despite using relatively little (grapeseed) oil: not so much to make the result greasy, but also not so little that food gets scorched and burns from direct contact with the bare pan.
If cleaning is not done promptly—if, for example, the pan is left with a thin (1 mm) layer of oil—the oil will tend to build a gummy, non-uniform, and non-polymerized layer that is hard to clean. Anything one uses to clean (even a stainless-steel chain cleaning tool) will become gummied.
Can you comment on this detail? Is this actually true? After a get-together when the kitchen looks frighteningly hard to clean, can one ever leave a cast iron pan for cleaning seven or so days later? Might it perhaps be sufficient to remove the excess oil before leaving for seven days? I can continue experimenting of course, but I'd rather hear expert opinion to reduce the number of these experiments.
If you do have a gummied cast iron pan, the only real solution is to leave it in the oven for one hour at 450-500F. (Lodge's website says so, and so it must be true.) I expected that the extra gummy oil will liquify and drip. Not so. It merely burns. I could then scrape the pan (until going back down to nearly the bare metal, wasting one year of seasoning), thinly oil, and bake again upside down briefly.