Cleaning the glass on a fireplace or woodstove can require a lot of scrubbing and elbow grease, depending on how thick the soot is. It will be easier to clean the glass if you maintain it properly and take steps to prevent the glass from getting dirty. You can also help keep the glass clear by practicing good fire-burning habits, and this will reduce the amount of time you have to spend cleaning the glass.

If you regularly have to scrub the glass then you should also be having your chimney swept every three months in use your chimney sweep can advice on this.

Step 1:
Lay a sheet of newspaper on the hearth under the door. Crumple a sheet for cleaning.

Step 2:
Wet the crumpled piece of newspaper.

Step 3:
Dip it in some wood ash. (no smokeless fuel ash this can scratch the glass)

Step 4:
Get scrubbing  recharge your newspaper with ash paste.

Step 5:
Finish by wiping the paste off the door with a clean piece of paper
For more stubborn stains a good quality ceramic hob cleaner e.g. Hob brite can be used.
Dispose of the damp paper in the bin.

Burn seasoned hardwood only. When clean fires are your priority, dry hardwood is the only fuel you should burn in your woodstove or fireplace. This will produce the hottest fire, will ensure all the fuel burns, and will help prevent smoke or soot. To prevent smoke, soot, and creosote buildup, never burn:

Wet or damp wood
Coal
Treated wood
Household Rubbish
Large amounts of paper