Hi, all. I just got my #3D smoker and I noticed that there is a black residue with some visible depth on the wire shelves. It will rub off on a paper towel, completely saturating it in black. I ran them through the dishwasher, but there was no noticeable change. I have been scrubbing at them with paper towels and a mild abrasive meant for glass cook tops. It is taking about 45 minutes to clean each shelf. Before I potentially waste any more of my day, what is this stuff (welding residue?), do I really need to remove it, and if so does anyone have any tips on how to do so with stuff one might have around the house? Thanks in advance for any advice.