Seasoning (cookware)

If it is not pre-seasoned, a new cast-iron skillet or dutch oven typically comes from the manufacturer with a protective coating of wax or shellac; otherwise it would rust.

Alternatively, for woks, it is common to burn off the coating over high heat (outside or under a vent hood) to expose the bare metal surface.

Then several times the following is performed: The precise details of the seasoning process differ from one source to another, and there is much disagreement regarding the correct oil to use.

When oils or fats are heated, multiple degradation reactions occur, including decomposition, autoxidation, thermal oxidation, polymerization, and cyclization.

The soluble glycerol then burns off creating (toxic) smoke while the fatty acids in the oil polymerise and harden.

Heating the cookware (such as in a hot oven or on a stovetop) facilitates the oxidation of the iron; the fats and/or oils protect the metal from contact with the air during the reaction, which would otherwise cause rust to form.

Some cast iron users advocate heating the cookware slightly before applying the fat or oil to ensure it is completely dry.

The surface formed is broadly speaking hydrophobic and oleophilic, but is more versatile in that it temporarily turns hydrophilic on contact with high-water ingredients.

[25][26][27] Tests conducted by America's Test Kitchen found that, while cooking a highly acidic tomato sauce for over 30 minutes produced a metallic taste, cooking acidic food in a well-seasoned pan for a short time is unlikely to have negative consequences.

[28][29][30][31][32] Cast iron pots are best suited to cook food high in oil or fat, such as chicken, bacon, or sausage, or used for deep frying.

Black oxide provides some protection against corrosion if also treated with a water-displacing oil to reduce wetting and galvanic action.