I’ve been writing about the wonders of cast iron cookware for 7 years now, so the fact that I could be surprised by anything at this point is amazing. But guess what? I’m surprised to find out that there is one product that could destroy your beautiful pan. You should never use this on your cast iron pan — Dawn dishwashing liquid.

I’m not knocking Dawn as a product, it’s a great degreaser. In fact, it has many uses outside of the dish sink. But the reason that Dawn is the cleanser of choice for removing oil from wildlife caught up in an oil spill is the very reason it is not good for cast iron.

When a cast iron pan is heated with a fat, an amazing transformation happens. The heat causes a chemical reaction in which the fat polymerizes, meaning that multiple individual fat molecules join together to form larger molecules. It is these larger polymer molecules that bind to the metal of the pan and form the seasoning. These seasoning molecules can’t be destroyed by scrubbing or even a mild soap.

But Dawn contains certain types of solvent agents and sulfides that are extremely effective at dissolving oil. A heavy degreaser like Dawn will bind to the oils in the skillet and strip them. This will disturb the seasoning, especially on a newly seasoned pan.

Those solvents that are so helpful when washing a Pyrex casserole crusted with lasagna, will remove the seasoning from your cast iron pan permanently, making it more difficult to get and maintain an even and durable seasoned surface. If you wash your pan with Dawn, you will need to re-season your cast iron. Plus, removing the seasoning can open the door to rust — something you don’t want to get a foothold on a cast iron pan.

There is some controversy about whether it’s necessary to ever use any kind of soap on a cast iron pan. I come down on the no-soap side. A well-seasoned cast iron pan is so slick and pore-less that there is really no need to use soap. A stiff brush and hot water is all I’ve ever needed to remove even the toughest cooked on bits.

Of course, I’ve had my pans for many years. They are indeed well seasoned.

But if you are just beginning the seasoning process, you may have the need to scrub your pan from time to time. And if you do have a stuck-on mess, I can see where you might want to use a bit of soap. But stay away from Dawn.  It will remove your seasoning and make it harder to keep your pans in good shape.

So, bottom line, never use Dawn on your cast iron pan. You might think your getting your pan cleaner, but in fact, you’re making it harder to create and maintain your seasoning. And that’s a big problem when your talking about a useful cast iron pan.