I purchased a 10" Lodge pre-seasoned cast iron skillet 3 months ago and have maintained it very carefully. I always clean with hot water, no soap, scrub with a nylon brush, dry, and apply an oil coat while the pan is still warm. Today I used my cast iron skillet to bake a few pizzas at 550 degrees F (plus broiler at times.) Some cheese, tomatoes, and herbs fell onto the skillet during this process. I cleaned the skillet in between pizzas the best I could with a damp towel. Afterward, I soaked the skillet in hot water for 20 minutes, scrubbed with a nylon brush, and then scrubbed with my fingernails wearing one of those yellow "rubber" dishwashing gloves. After drying and coating the pan with oil, I saw some black residue on on my hands (I applied the coat with my bare hands.) I noticed there were some ashy spots on the pan. No matter how many times I scrub and rinse, there is still residue coming off the skillet.
I have read quite a bit, but I'm unsure if I should simply not worry about a little ash, keep trying to clean it, re-season the pan, or strip the seasoning and start all over. Any ideas?