If you are sensitive to CI and power tools, you should stop reading now.
All,
I have a Griswold 5 Block SB that I cleaned. After lye, there was a spot on one side of the pan that seemed like the gunk just was not coming off. More time, stepped up the lye. Looked entirely like a nice Griswold iron, smooth, no rust, right color after lye and wash (dark grey), no sulfite burn, etc. Except for the spot, which did not change further. A little discolored, and looked flakey, but did not want to clean up.
After a heavy scouring and through inspection and a bit of scrapping with a knife, I concluded that what ever it was, it was not going to come off, and that the skillet was destined to be a user. With that in mind, I set off to improve it's utility with a Dremel.
The center of the affected area at first acted somewhat like heavy seasoning, grit coming off rather brown until I got to bare metal, polished smooth. However, when I tried to feather the polished area to the rest of the skillet, it became apparent that whatever the rough flakey spot was, it actually was covered the entire pan surface, continuing into the seemingly normal surface with no distinct transition. Recalling that the entire skillet was good-looking, seemingly-normal black/grey iron that seemed normal in every other aspect, is anyone aware of any coating hard coating (not a basic oil pre-seasoning) applied by Griswold that looks like black grey iron, but isn't? BTW, this coating did not look or act like enamel.
I concluded that the spot was in effect a delamination, but have no idea what the coating or material is.
The skillet ended up being smoothed across the bad spot, cleaned and heavily seasoned, and currently residing in the kitchen. Sorry no pic prior to seasoning, this was some months ago.
