The cleaner will loosen up the hardened grease. Scrape the oven with steel wool once the oven has cooled down.
[header] How to kosher an oven [title] Use a caustic oven cleaner. [step] Begin the koshering process by spraying a caustic oven cleaner inside of your oven. Leave the oven on for as long as the instructions recommend after you've finished spraying the oven with the cleaner.