I just did the nasty today cleaning out both of my flue liners for my pellet stoves and my classic bay liner was in really good shape with some light gray/brown ashing when I brushed it out. When I cleaned the castile, it had a ridiculous amount of thick, black ash in the liner. I mean a massive amount. I'm assuming that the classic bay is burning correctly, but what would cause that much ash and make it black? Both burned the same pellets.