To clean a glass fireplace screen, you may need to add an extra step or two to the glass cleaning process. In the end, however, it’s much like cleaning regular glass.
Scrape Off the Hardened Ash
For heavy buildup of baked on ash, first use a flat razor blade (do not try this with a utility knife, since you won’t be able to put it flat against the glass) to scrape the soot. Begin in one corner and work your way across the screen. Hold the blade at an acute angle, nearly flat against the glass, to avoid scratches.
Remove the Softer Ash Build-Up
Many find success removing soft ash buildup on a glass fireplace screen by using dampened newspaper dipped in fireplace ashes. Rub the newspaper in a circular motion on the glass, then discard and begin again with another piece of newspaper. This will remove much of the buildup from the glass.
Clean With Ammonia
A solution equivalent to ¼ cup of ammonia in 1 gallon of water is a great cleaning solution for glass. If you have any greasy buildup, add a few drops of dish soap to the mixture. Apply with a soft cloth or spray and wipe with newspaper, cloth, or paper towels.