Silicone mats are a boon to baking, but after time, they tend to develop a greasy layer that never wants to come off. Soak your mat If your mat is super greasy or has cooked-on particles stuck to it, soak it first. Fill your sink with super hot water and grease-cutting dish detergent. Let the baking mat soak dirty-side down in the water for 10 minutes, then put on some thick dishwashing gloves...