Smoke Chamber Seal
If you are not familiar with the set up of your masonry chimney, you may not know about the smoke chamber. This is the part of your chimney between the damper and the bottom of the flue. Its walls should be smooth and parged allowing smoke to easily roll up to the flue without obstruction. When the smoke chamber does not meet these specifications or it has lost its integrity, a parge coat of ceramic mortar is applied to seal and smooth the chamber.