- Dark soot type
- Gray or white film type
Dark soot like stain
Glass doors or fixed glass on fireplaces often develop a dark type discoloration on the glass. Generally referred to as “soot.” This soot may be from the gas not completely burning resulting from the position of the gas logs, gas pressure or the burner settings.
Burning wood logs may also cause a dark build-up. If the wrong type of wood is used or the drafting is not proper, then a dark discoloration may occur on the glass. Another reason for soot, is that the fire is not burning hot enough, i.e. not enough combustion air (so check to make sure the damper is in a full open position).
Gray or white film on glass
A gray or white film on the glass is usually from the chemical residues in the gas that gather on the glass. This is not un-natural. When burning fossil fuels, such as wood or natural gas, there is a by-product in the combustion process that results from burning these fuels. It is sulfur. When sulfur is combined with moisture in the air, it become sulfuric acid. This will stain (give a gray or whitish look) or etch the panels overtime. Cleaning the glass doors or panels on a regular bases makes for a good home maintenance item.
Fogging of glass
When a fireplace is first lit, the glass panels or doors may fog over. If you wait a little period of time the fog disappears. Usually this is merely water vapor that comes from the burning of natural gas. When the warm air with water vapor hits the cool glass, a thin film of condensation occurs; the glass looks foggy. As the glass heats up, the moisture on the glass re-evaporates and becomes clear. Each time there can be a little residue left over, so cleaning from time to time will help keep the glass clearer.
If the fogging does not go away, then checking the venting system would be a good idea.
Cleaning the glass one to three times a year is generally sufficient. If the fireplace gets heavy use, then cleaning it more often is a good idea.
When cleaning the glass, try to avoid cleaners with ammonia in them. Water with a little vinegar will often work. Harder stains may require special fireplace glass cleaners designed for stains.
After cleaning, check:
1. If there is a gas line (pipe) coming through pre-manufactured panels on the side of the interior firebox, then is it sealed around the gas line pipe where it goes through the panel. (read more about this safety concern)
2. Check to see if the fireplace has or needs a damper clamp. If so, is it installed properly and working properly? (read about damper clamps)Who to consult? Fireplace companies, as well as some chimney sweeps and handymen.
Home owner generally do the majority of the cleaning and maintenance on fireplace glass doors. Fireplace companies, as well as some chimney sweeps and handymen do this type of work.