Frequently Asked Questions
Cast Iron Care/Rust issues and prevention
Pre seasoning, the “coating” is heated soy oil, the same used on dutch ovens and lodge pans. When vegetable oils, lard, crisco, bacon fat,... get heated they polymerizes, i. e. turn into a sticky goo. First yellow, red, then black. It protects from rust and provides the non stick properties pre seasoned cast iron is known for.
But since it is just "dried" oil, its not as durable as enamel or powder coating and needs to be preserved and maintained. Heat will burn it off, moisture will soften it and acid will eat away at it. Ideally you close the vents after grilling to snuff out the coals and come back a while later, do a quick scrape with a spatula, if grey, oil a bit with a paper towel, sweep the ash out and leave just a bit open. Of course doing it after every cook is not always possible, but the longer the grates stay unprotected(unoiled) in hostile environment(humid and gunky) the more tlc is required before the next cook. Humidity softens the coating and makes it gooey, till eventually the moisture reaches the iron below. If you’re not grilling for some time, brush thoroughly and oil before storing the grill. Leave the bottom vent open for airflow to reduce moisture. Ash in the grill and old coals will attract moisture, this might be more severe if you live somewhere humid. Sweeping the ash out and leaving the bottom vent open for air circulation prevents that. Gunk will eat away at the seasoning(tomato and vinegar for example are acidic). I scrape with a cheap hardware store spatula, most gunk will just flake off. Brush a bit before grilling.
The residue/gunk left on the preseasoning after your last cook is acidic and will eat away at it, there is acid in sauces or tomatoes High heat will burn it off. Most non fatty things like steak, chicken breast are grilled over high heat, you will notice the color change from black to dull grey after a few cooks. Brush the grates with oil or crisco and the black will come back. It also helps to alternate the inserts that sit over the fire. If you grill fatty foods as well, sausages, winge, porkshoulders, then this should be no problem. Should your grates be rusty, heat them and brush afterwards. You remove the old coating and the rust, oiling fills the metal pores to prevent rust again and heat will turn it back into a protective goo. Light one chimney of charcoal, Take out the inserts and dump the coal evenly in the 4 openings. Put the inserts back, close the lid and completely open top and bottom vent. Heat the grate at full power for maybe around 45 min. Brush with a stiff brush, dip a papertowel in vegetable oil and oil the grates with your tongs. They ll be black again. Ideally you grill some fatty foods once or twice, bacon wrapped or chicken wings, ideally pork shoulder. And they will look like new.