Dan I think I know what your are talking about but a picture would help??  Assuming that the pieces are cleaned and not seasoned there are just some places where there will be darker spots and the iron appears to be stained??  Otherwise you could try rinsing the piece with cold water and wipe it with paper towels until it is clean.  You will get a whole bunch of black stuff off the piece and it will not stop coming off until the piece is dry??  If this doesn't help you out just keep firing away at the questions!!

Sam I never thought of that??  I was thinking that the piece was totally clean but you might be onto something!