Seasoned cast iron
Bare iron protected by a baked-on oil layer. Water is the enemy, not detergent — and the manufacturer says so more plainly than the folklore does.
What not to do
Soaking is unsafe on Seasoned cast iron
Unsafe
Do not do this. The risk is established, and it is described below.
The one thing the manufacturer is unambiguous about, and the opposite of the technique it recommends for almost every other burnt-on deposit.
Precautions
- Check the manufacturer's instructions
Evidence
Supported
Sources
How to Clean seasoned cast iron
Lodge Cast Iron (Lodge Manufacturing Company) · Manufacturer documentation
Relied on for: That soaking cast iron in water is a recipe for rust, and that a dishwasher will remove the seasoning and likely cause rust. (states this directly)
Precautions
- Check the manufacturer's instructions
In detail
Seasoned cast iron is bare iron carrying a layer of oil polymerised onto the surface by heat. Everything about caring for it follows from those two facts: the iron rusts readily when left wet, and the protective layer is organic rather than metallic. The best-known rule about it is the one the manufacturer contradicts. Lodge states that soap is entirely acceptable, because the detergent sold for washing dishes today is no longer strong enough to remove seasoning — the prohibition was formed around the caustic soaps of an earlier era and has outlived them. What the manufacturer does prohibit is water left in contact: the dishwasher removes the seasoning and will likely cause rust, soaking is described as a recipe for rust, and air-drying rather than towel-drying is listed among the things that cause it. The routine is therefore short and its order matters — wash, dry completely, then oil thinly while the pan is still warm. Rust is recoverable rather than terminal: a metal scrubber is acceptable for removing it, though not for daily cleaning, and heavier corrosion means re-seasoning rather than replacement. Enamelled cast iron is a different material and none of this applies to it.
Properties
Sensitivity
- Acids
- Not known
- Alkalis
- Not known
- Chlorine bleach
- Not known
- Heat
- Not applicable
- Abrasion
- Sources disagree
- Porous
- Not applicable
“Not known” means nobody has established this, not that the material is unaffected.
What works
Detergent is safe on, in specific conditions, Seasoned cast iron
Safe only in specific conditions
This is only appropriate within specific limits. Outside those limits, no claim is made.
Only within these limits:
- Ordinary washing-up detergent, by hand, not in a dishwasher
- Do not leave the pan to soak
- Dry completely immediately afterwards, then oil thinly
The manufacturer's position is that modern dish detergent is no longer strong enough to remove seasoning. The prohibition people remember was formed around caustic soaps that are no longer sold.
Precautions
- Check the manufacturer's instructions
Evidence
Supported
Sources
How to Clean seasoned cast iron
Lodge Cast Iron (Lodge Manufacturing Company) · Manufacturer documentation
Relied on for: That soap is acceptable because the soap used for washing dishes today is no longer strong enough to remove seasoning from cast iron, and that the routine is wash, dry completely, then oil. (states this directly)
Why
- Seasoned cast iron is explained by Corrosion and passivation
By contrast with stainless steel: the protection here is an applied organic layer, not a self-repairing oxide film.
Related
- Seasoned cast iron is commonly affected by Rust
- Seasoned cast iron is commonly affected by Burnt-on food and carbon deposits
Aftercare and prevention
- Rinsing and drying requires the aftercare Seasoned cast iron
Drying is not the end of the job on this material — bare iron needs re-oiling before it is put away.
- Neutral cleaning requires the aftercare Seasoned cast iron
Hacks and claims involving this
- Never use soap on cast iron Does not work
When the obvious answer is wrong
Can I leave a cast iron pan to soak to get the burnt-on food off?
Cast iron is bare iron protected by a layer of polymerised oil, and that protection is defeated by water rather than by scrubbing. The manufacturer's wording is blunt: SOAKING CAST IRON IN WATER IS A RECIPE FOR RUST. It extends the same warning to cookware left in the sink to soak, put in the dishwasher, allowed to air dry, or left in a moisture-prone environment — and states that a dishwasher will remove the seasoning and likely cause rust. The failure is not the burnt food coming off. It is that the pan is left in prolonged contact with the one thing its finish exists to keep off it.
A different kind of treatment works: Substitute mechanical action for time, and then remove the water immediately. The manufacturer's routine is three steps: wash with warm soapy water, scrubbing with a stiff-bristled brush or a scrubbing pad; dry COMPLETELY with a paper towel or lint-free cloth; then add a thin layer of oil distributed over the entire surface. Note what is permitted, because it contradicts the folklore that grew up around this pan: soap is explicitly fine, on the stated ground that dish detergent today is no longer strong enough to remove seasoning, and it prevents build-up. Air drying is not an option — it is listed alongside soaking and the dishwasher as a way to get rust. Where rust has already formed, steel wool or a metal scrubber is acceptable to remove it, though not for daily cleanup. This damage is recoverable in a way most surface damage is not: a rusted pan can be scoured back and re-seasoned.
Sources for this page
Sources
How to Clean seasoned cast iron
Lodge Cast Iron (Lodge Manufacturing Company) · Manufacturer documentation
Relied on for: That soap is acceptable because modern dish detergent no longer removes seasoning, that a dishwasher removes seasoning and likely causes rust, that soaking is a recipe for rust, that the routine is wash then dry completely then oil thinly, and that steel wool is acceptable for rust removal but not for daily cleanup. (states this directly)