I'm burning about three splits of oak about four inches in diameter at most,two about four inches apart and the third straddling them.I'm burning them at the rear of the stove placed east to west. A super cedar gets them going and unbelievably to me the temp gets as indicated by the stovetop thermometer to about 650,and the cat probe reads close to 1500,I achieve this with the stove set at three,I burn about an hour this way and then shut her down to 1.5 sometimes 2 these splits burn and throw heat easily 15 hours. The problem is I get a chocolate coating on the glass in a V shaped pattern,on this pattern are some minute black flakes. This stuff is very hard to clean,is this typical with the BK,is it possible my oak is not fully seasoned? Three years in a covered shed. Should I burn these small amounts in front of the stove door? Any help would be much appreciated. This is my first cat stove and about six weeks old. Thanks in advance.