Got some valor blocks whipped up. Pressed the first one, only to see a "lovely" brown smudge on the white center appear. Looked at my iron's plate, and sure enough - somebody had got something on it. Rats. (Must have been rats, because I sure didn't do it <heh>, and my daughter and hubby plead innocent, too!)
I recalled hearing something years ago about rubbing wadded up waxed paper on the hot plate, so I thought I'd give it a go. Wow! It sure did work! Took those brown patches right off. I can see, though, that you want to be EXTRA careful not to burn yourself!
Oh, the valor blocks? Here they are: