Why Do You Not Use Soap on Cast Iron?

The idea that you don’t use soap on cast iron dates back to the days when household cleaners were made with harsh ingredients like lye and vinegar, which can strip the seasoning and damage the pan’s underlying iron. Today, however, modern-day soaps are much gentler, and a little bit goes a long way toward keeping your cast iron clean and well-seasoned.

The Reality

A properly seasoned cast iron skillet has already been rubbed with oil repeatedly and heated so that the oil breaks down into a polymerized substance that bonds to the surface of the metal, giving it its non-stick properties. The surfactants in today’s dish soaps won’t affect this layer of polymerized oil, so it shouldn’t matter if you wash your pan with soap.

The Myth: That Soap Can Damage the Seasoning

Some sources suggest that soap can harm the seasoning on a well-seasoned cast iron skillet because it is designed to remove oils. But as Serious Eats points out, this isn’t true.

Rather, the problem is that soap can dissolve away the oils that protect the seasoning, and permit water to get into the pan, which could result in rusting. This can then destroy the seasoning on the bottom of the pan.

In addition, the surfactants in soap can cause a chemical reaction with the lipids (fats) that form the layer of protection around cast iron when it is seasoned. This reaction results in a break down of the lipids, which then can lead to rusting on the cast iron.

So if you want to clean your cast iron, the best thing to do is give it a good scrubbing with kosher salt and then rinse it off thoroughly with hot water, leaving no residue behind. Then, let the pan air dry and rub a light coating of oil on it before storing.

If you follow this simple cleaning procedure, your cast iron will last for years and will never have to be re-seasoned again. But if you don’t take care of your cast iron, it can quickly start to show signs of wear and tear, such as food sticking to the cooking surface or rusting.