Clean silicone baking molds (fatty film): boil in salted water
Silicone molds have the peculiarity of holding the fat down properly ... that is, after baking you can wash and clean as much as you want, if you want to use the clean shape next time, it's always kind of greasy.
This is not a quality defect and has nothing to do with dirt, it is simply due to the material, this silicone absorbs the shortening downright. If that bothers you: cook the silicone baking dish in salted water, then you will not have this shortening oil film any more.
