Hello, Everytime I clean the glass on my stove (lopi liberty) it gets dirty again fast within 4 to 5 hours and gradually worse as it burns longer to the point where it is a black layer over it by morning, I have airwash on my stove but it seems like that its not working. I am burning 1 to 2 year old seasoned wood, my chimney is about 22ft. tall so I dont think it is a draft issue but possibly? I am wondering if this is normal? and it seems to happen alot faster when I start to shut the air down on it, I never shut the air all the way down though.