In most cases, the following instructions can help restore the nonstick coatings.
A dark build-up on the surface of the pan indicates oil carbonization. This build-up occurs over time when cooking oil is used above its smoke point - extra virgin olive oil or butter is the usual cause. The oil doesn't damage the pan, but it can be tough to remove. We recommend trying a paste of baking soda and water:
Baking Soda Treatment for Nonstick Cookware
1. Mix a solution of baking soda and water about the consistency of toothpaste.
2. Rub this solution into the pan wherever you see the dark build-up.
3. Scrub vigorously with a non-abrasive sponge.
4. Rinse, clean, and wash with hot soapy water.
5. Repeat as necessary.
Choosing an appropriate cooking oil and washing your pan thoroughly with hot, soapy water each time you use it will prevent this problem.