Cast iron cookware — whether a Japanese tetsubin (teapot), a nabe (hot pot), or a Western skillet — requires seasoning to perform at its best. The process is the same regardless of the vessel.

What is Seasoning?

Seasoning is a layer of polymerized oil bonded to the iron surface. It’s not oil sitting on top — heat breaks the oil molecules into a hard, plastic-like coating that fills the iron’s porous surface.

Initial Seasoning (Oven Method)

For new cast iron or stripped cast iron:

  1. Wash with hot water and mild soap (yes, soap — modern dish soap won’t damage bare iron). Dry thoroughly.
  2. Apply oil: Rub a thin layer of high-smoke-point oil (grapeseed, flaxseed, or canola) all over the pan. Wipe off as much as possible — the pan should look dry.
  3. Heat: Place upside-down in a 200°C (400°F) oven. Put a baking sheet on the rack below to catch drips.
  4. Bake: 1 hour. Turn off the oven and let cool inside.
  5. Repeat: 3–4 times for a durable initial layer.

Maintenance Seasoning

After each use:

  1. Wash with hot water — use a stiff brush or chainmail scrubber for stuck food
  2. Dry thoroughly on the stove over medium heat (to evaporate all moisture)
  3. Apply a microscopic layer of oil — warm the pan, rub oil in, then buff dry with a paper towel

Common Mistakes

  • Too much oil — Creates sticky, gummy patches. The pan should look dry after oiling.
  • Acidic foods — Tomato sauce, wine, or vinegar degrade the seasoning layer.
  • Soaking — Water causes rust. Never soak cast iron.
  • Dishwasher — Never. The detergent and high heat strip seasoning.
  • Metal utensils — Acceptable on well-seasoned pans, but wood/silicone extend the seasoning life.

When to Re-Season

If food starts sticking, or you see rust spots: light scrub, dry, single oven seasoning cycle. For heavy rust: full strip and reseason.

Sourcing: Seasoning science based on JIS (Japanese Industrial Standards) for cast iron cookware surface treatment. Temperature and oil recommendations verified against published data from Japanese cast iron manufacturers including Iwachu (iwachu.co.jp).