What Is This White Haze on my Viewing Window?

Q: The viewing window on our gas stove has developed a whitish coating on the inside that won't come off. I've tried Windex, ammonia, you name it. What is this stuff, and what can I do about it?

A: Thanks for the inquiry! The whitish haze you see is the result of hard water deposits, which aren't a direct result of gas combustion: they occur due to condensation. You may have noticed that whenever you light up a cold gas stove, water vapor condenses onto the inside surface of the viewing window, causing a "fog"that dissipates rapidly as the glass heats up. Over time, mineral deposits just like the ones that you find inside teapots build up, causing the cloudy appearance you describe.

If you've ever tried to remove water deposits from a teapot, you know how stubborn they are. They must be polished off, using an abrasive cleaner that more resembles Brasso than Windex. Gas appliance window cleaner, available at hearth product stores, contains much finer abrasives than metal polish so it doesn't scratch the glass. The brand we carry is made by Heat Safe, and is called 'Gas Stove and Fireplace Glass Cleaner.'