Yeah, you're right about the chill mix-up. Seen that white iron happen when the mold was too cold before the pour even started. On those big gears, if the sprue starts to crust over, that's when you gotta pour like your life depends on it.

Seriously, @wendy978? Three times already?

Actually, that warped board might be fixable! Putting it under some heavy books for a few days can flatten it out pretty well. I had a Monopoly board that was a total mess, and that method saved it. Just make sure the room isn't too humid when you try it, or it'll just warp again. Would be a shame to use a game board as a coaster if it can be saved.