After use, grill pans can accumulate soot from burned food, grease and cooking oils. Soot is made of carbon and ash. This material can be brown to very black, thick and chunky or a greasy film or residue. The higher the cooking temperature, the more soot will appear. Cooking fires and gas yield more soot than electric stove tops because soot also builds up as a byproduct of flames. Washing a grill pan in a dishwasher intended for home use will result in soot accumulating within the dishwasher pipes and tubes and other working parts. Black or brown spots, residue and film may coat the dishwasher racks, interior door and compartment. Washing dishes, after washing a grill pan, may result in dishes coated with an oily, sooty film for many subsequent washing cycles.
Most home hot water heaters are adjusted to 120 degrees Fahrenheit. A household dishwasher may reach temperatures of up to 140 degrees Fahrenheit. Even at the higher temperature, the water is not hot enough to eliminate soot from the fat proteins grilled on the grill pan. The greasy black film remains behind inside the dishwasher instead of being washed away during the wash and rinse cycles. This lack of sufficient heat to successfully remove soot from fat proteins is a reason not to wash the grill pan in the dishwasher.
Knowing about water temperatures and dishwasher contamination doesn't help you much after the fact. If you've washed your grill pan in the dishwasher, you can eliminate the greasy, oily black residue and film left behind. Remove the grill pan from the dishwasher. You can leave the dishwasher racks, utensil basket and even other affected film-covered dishes. Fill the main detergent compartment with dishwasher detergent. Add 8 tablespoons (4 ounces) of citric acid to the secondary detergent compartment. Run the dishwasher as normal. Citric acid is a natural cleaning product derived from citrus fruits and vegetables. Use citric acid with caution as it may irritate skin and will irritate and burn eyes. Citric acid is available from organic food distributors, online resources and in grocery stores and some pharmacies. After washing, reset the dishwasher to a rinse-only cycle to flush any citric acid from the appliance. In the event that any film remains, scrub the area with undiluted vinegar and a sponge and repeat the citric acid application.
Properly clean cast iron grill pans by hand. Spray the soot-laden pan with oven cleaner and allow the pan to sit for about 10 minutes. Use caution, when handling oven cleaners, as they can irritate the skin, respiratory tract and eyes. Place the pan in the sink or a bucket and use a wire grill brush to scrub the soot from the pan. Soak clean rags in olive or vegetable oil and use the rags to wipe the soot and residue from the pan's interior and exterior. When the pan is wiped clean, use a clean, oil-saturated rag to rub the inside of the pan. Wash nonstick grill pans in hot, soapy water and scour them with nonstick coating-safe scrubbers.