A well-cared-for cast iron dutch oven will retain its seasoning and continue to be useful for generations.
Cleaning a dutch oven entails two steps: Remove any food left in the dutch oven, and maintain the dutch oven’s seasoning.
1. Remove any leftover food:
I’ve heard of people using everything from harsh detergents to metal spatulas to river rocks to scrub out a dutch oven. Any kind of soap put into a warm dutch oven can seep into the seasoning. This can weaken the seasoning. The soap can come back out of the seasoning and add unwanted flavors to the next meal. Harsh treatment of the oven (with things like steel wool, metal utensils, or river rocks) can scrape away the precious seasoning and the oven will need to be babied, or even re-seasoned.
It is important to not let food or water sit in the dutch oven for a long time. It can erode the seasoning and will lead to rust and re-seasoning. Once most of the food has been taken out of the oven, the remaining food can be removed with hot water and a stiff brush. Lodge Manufacturing sells a synthetic-bristled brush that works very well for this purpose. Stubborn, stuck-on food can be coaxed off using heat and/or a plastic scraper. Leftover cooking coals or a nice camp stove can be used to apply heat.
At the same time, any residual ash from the coals used in the cooking process should also be scrubbed away. The stiff brush works wonderfully for this purpose as well.
Once all of the food is removed from the dutch oven, towel dry it thoroughly, removing as much water as possible.
2) Maintain the seasoning:
While the oven is still warm, apply a very thin coating of vegetable oil (or cooking spray, according to Lodge Manufacturing) to all surfaces of the dutch oven, both inside and out. It is best done while the oven is warm because the pores of the cast iron and the seasoning will be more open and receptive to the oil. Don’t use so much oil that it pools inside the oven or on the lid. Excess oil can be absorbed with paper towels.
The dutch oven is now ready to store until its next use.
The oven should be stored with its lid slightly ajar to allow air circulation. I like to place a paper towel in the bottom of the oven (to absorb any excess oil or moisture) and I wedge two or three folded paper towels between the oven and the lid.