I grew more cucumbers then we could eat on a metal trellis last year and I didn't notice any signs of burning.

I use an amount of charcoal that will be about 2 coals high when it's ready to use and spread out. Until charcoal is ready to use, you don't want to shut the lid, the fumes need to burn off first. As long as it still smells like lighter fluid, the lid should stay open. Using more than you really need is never a bad accident, but not enough can ruin your dinner. Err on the side of too much. When you're ready to cook, you can close the lid and adjust the vents to prevent flare-ups. Open more = more air, hotter fire, charcoals don't last as long. Usually we'll have the bottom vent barely cracked and the top vent about double that. 250 is plenty hot enough to cook about anything, probably too hot for thicker piece of chicken that would be burned on the outside before the inside was done. The temperature a few inches above the coals is much hotter if that's what the lid thermostat says (which I don't put much faith in, easy to find a cheap oven thermometer to set in a corner to check it.) Meat thermometer is a good idea to have so you don't have to guess or judge by appearance. Once you've used it a few times, you'll get more comfortable and "good" at it.

Hope you have good ventilation in there, open window, ammonia in small space can cause chemical pneumonia, (you will get dry throat, feel thirsty,can't get enough to drink if you are getting a reaction. I had it & took 3 mos. to get over. I was in hall cleaning with a spray "Top job" I think it was called, I kept closing doors until I was in a space about 6 ft by 4 ft. There were 5 doors & I closed them as I got each 1 finished, should have been opening them for more air circulation. GF cleaned a small bedroom on rainy day with windows closed& she also got pneumonia. She was just using water with ammonia in it. Ammonia is extremely dangerous when mixed with Comet or other cleanser that has bleach in it. It causes gas that will kill you. My cousin was a fireman, he pulled guy out of meat dept that had used that at major chain store he was unconscious but he lived, fireman just barely made it out with him as it got to him too. That chain stopped doing it that way. Comet & bleach are dangerous when mixed also.It may have been the comet & bleach mix that knocked the guy out.It was at least 30 yrs ago. Forms hydrochloric acid I think, can't remember my chemistry that well. Be careful!

Thanks! I appreciate the suggestion of the thinner. I hadn't thought of that. It is not unfortunately natural variation in the wood-I think sombreuil hit the nail on the head about too much wet mopping. Oil certainly could be holding dirt-but then wouldn't I be able to get the dirt off? I have tried everything. I did sand a small spot in the pantry and it did seem to come off with sanding, so it's not the wood. Thanks again! I would have come back sooner but I didn't get the notifications that I had replies so I thought no one had any ideas. Appreciate it!