Yes, you can definitely season an old cast iron skillet again to make it usable. Seasoning is the process of applying a layer of oil to the cast iron's surface and then heating it to create a protective, non-stick coating. Over time, this seasoning layer can wear off or become damaged, but it can be renewed to restore the skillet's cooking properties.
Here's how you can season an old cast iron skillet:
Clean the skillet: If the skillet is dirty or has any rust, clean it thoroughly. You can use hot soapy water and a non-abrasive sponge to remove any debris. If there is rust, follow the rust removal steps mentioned in the previous response.
Dry the skillet: After cleaning, make sure the skillet is completely dry. You can towel-dry it or place it in a warm oven for a few minutes to ensure all moisture is gone.
Apply a thin layer of oil: Use a high-smoke-point oil like vegetable oil, canola oil, flaxseed oil, or grapeseed oil. Avoid using low-smoke-point oils like olive oil as they can create sticky residues. Apply a thin, even layer of oil to the entire surface of the skillet, inside and out, including the handle.
Remove excess oil: After applying the oil, use a clean cloth or paper towel to wipe off any excess. You want a very thin layer of oil on the skillet.
Preheat your oven: Preheat your oven to around 350°F (175°C).
Bake the skillet: Place the skillet upside down on the top oven rack, with a sheet of aluminum foil or a baking sheet on the bottom rack to catch any drips. Bake the skillet for about 1 hour.
Cool and repeat: After an hour, turn off the oven and let the skillet cool down inside. You can repeat the seasoning process 2-3 times to build up a more robust seasoning layer.
It's important to note that seasoning is an ongoing process. Regular use and proper care will help maintain and improve the seasoning over time, making your cast iron skillet more and more non-stick and durable.
If your skillet has a thick layer of rust, pitting, or severe damage, it might not be salvageable. In such cases, it's best to consult a professional or consider replacing the skillet. But for most old cast iron skillets that are in reasonably good condition, re-seasoning will make them usable and bring back their excellent cooking properties.