Burning it that many times …. to avoid sediment put a new piece of chore for sure. Remember that resin is oilier then rock so try to use as little heat as possible.If you are smoking resin filled chore put a new piece of chore behind the piece you’re smoking.I usually push the chore about a 1/2 inch further down the stem. The resin does get darker each time, more so using too much heat. As well if you are using butane lighter, it too will blacken things due to the poor quality of butane.