i cleaned the chiminy yesterday,,clay type,,and had a glass looking creosote about 3 ft or so down--i usually have crust at the top about a half inch by mid winter,,also only a few feet down---this fall i added 2 ft to the chiminey---but what is the glass looking stuff--it did not come off as easy as the crusty stuff last year,,as a matter of fact it was not peeling off, just scratching it---its about 1/16 of an inch at the worst spot at the top--should i be worried? please help--am i still safe??---thanks