The problem with wood burning fireplaces is that overtime your fireplace glass begins to darken from the smoke residue. After a while you cannot even see the flames and loose the ambiance of the fire. This is an ongoing problem throughout the winter, so you need to find a fireplace glass cleaner that will remove the dark residue from the glass doors.
Fire glass cleaners are a dime a dozen, they claim that there's a specific product out there for only this application. In reality I have stumbled on a product that will not only clean my fireplace glass, but will clean my shower doors outside windows sinks and much more.