If you can not physically remove the seasoning that is still on the pan, what Tom Lehmann has recommended in the past for removing the carbon is a product known as Carbon-Off (http://www.acemart.com/janitorial/cleaning-chemicals-and-supplies/equipment-cleaners/16-oz-carbon-off-heavy-duty-degreaser-each/prod8275.html?cm_ven=google_base&cm_cat=Non-Cost_Listings&cm_pla=janitorial-gtcleaning-chemicals-a