I was experimenting with my new insert and had no luck with keeping my glass clean. Bought " best firewood around " using craiglist . Needless to say its hardly less than 25% if I'm lucky. Just ordered 4 tons of Bio Bricks and looking for relible source of firewood. Was experimenting with some bricks and fire wood mixes. Had couple nice fires with secondaries and cat converter glowing. Couple hours later still got black glass. I understand it's related to wood most likely. Or may be it's me shutting air too soon or else. What is your routine with bypass and air intake ?