Had some NEWP left over from last season. Burnt a few bags OK. Then they started to turn the glass black and noticed a lot of smoke from chimney. Thought it might be stove but no adjustments made any difference. Emptied out the hopper and loaded it up with Fireside Ultras. What a difference. Nice clean burn no smoke. So i am going to mix the two to get rid of the NEWP pellets. Five bags left of the NEWP.