Mix water, vinegar and baking soda gently in the stained pan with the spoon. Take care not to scrub the surface of the pan.
Simmer mixture over a very low heat for 15 to 20 minutes. Monitor water level carefully and add more as needed to prevent the solution from drying out in the pan.
Remove pan from heat and drain solution into the sink. Do not rinse.
Scrub stain gently with nylon scrubbing pad. The stain easily should scrub away.
Repeat process if part of the stain remains. Do not try to scrape off stubborn stains as this can damage the cookware.
Dry the clean pan and rub oil over nonstick surface to reseason the pan.