A certain amount of dirt and some occasional blackening on the glass of your heater is normal but it should not be going completely black as shown in the picture to the right!
Blackening of glass can occur for a number of reasons:
Burning unseasoned wood
All hardwood should be seasoned (cut, split and left to air dry for at least 12 months) to allow the moisture level to drop to around 20% or below ideally. You can check this with the moisture meter provided with your wood heater.
Burning unseasoned wood means that energy is used on evaporation rather than burning. This causes an incomplete burn and results in excessive smoke being produced. This settles in the form of soot, tar and creosote inside the flue system and of course on the glass.
Incorrect use of the air control
Everyone’s house is different, altitude, flue length and proximity of the flue to surrounding buildings and trees. Therefore you need to understand to what level and at what time your can adjust the air control.
All of the timber should be fully burning before you attempt to close the air control. Gradually adjust the air control to slow the burn rate after this point. Remember that if less oxygen is fed into the fire then it will burn cooler and if the wood is not ignited then creosote will form.
Fuel touching the glass
If the glass is blackening in just one or two areas rather than across its entire surface, it might be that logs may be too close to the glass, causing the fuel to burn against the glass.
Not burning hot enough
If the heater is not burn at an optimum temperature (Eg. if you’re trying to have a small fire burning in a large heater), the heater might not get up to a hot enough temperature for the airwash to function correctly.
Poor draw on the flue
If you have followed our instructions, and watched our videos on living with your Lopi and checked all of the above to rule out other causes, the problem might be the result of poor draw. In other words, the movement of air from your room, into the heater and up the flue is not powerful enough.
The poor draw might lead to smoke lingering in the firebox, because it is not being ‘pulled’ up the flue.
Poor draw can be a result of a blockage in the baffle or flue pipe, incorrect installation of the flue or down drafting as a result of obstructions around the outside of the home, too short of a flue or even a lack of oxygen in the home to feed the fire.
Consult your Lopi specialist for further advice.