The pyrolisis glass is a ceramic glass that is self-cleaning. A thin and invisible coat of metallic oxides is put on the outer side.

The radiation that comes from the combustion reflects on this side and causes an increase of the temperature of the glass,
inducing the pyrolisis of the tars on the internal side.

Thus it is important to increase the combustion to get the pyrolisis of the tars. An insufficient speed of the fire, an abnormal draught
(insufficient or excessive), an insufficient quality of the wood, a high hygrometry of the wood (more than 20%) can make the pyrolisis
less efficient.

Any obstacle to the radiation of a type of voluminous firedogs can also lead to bistre marks.

The outer side of the glass, the one that has been treated, has to be cleaned only with soapy water.
The inside of the glass can be cleaned with products especially
for fireplaces (that you can find at your seller’s or in a hardware trade).

Caution ! Never use any caustic or abrasive products. The presence of sulphur can destroy the transparency of the glass.
So do not use any sulphured fuel to start the combustion. Please check the composition of the fire lighters before using them.