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Q: The greasy smudge in the photo is on the door from my kitchen to my porch. It keeps appearing in the warm months and has been doing so for well over a year. No matter what I clean it with, it does not stay away for longer than a day or so. Do you have any idea what this is and how I can get rid of it? —Jacqueline Karch
A: How mystifying to be haunted by a seasonal smudge! It’s probably due to several causes acting in concert, over time.
- Harsh cleaning products can burn (or etch) glass, and squeegees and scrubbers can also cause scratches that can contribute to the sort of smudging you describe. For this reason, I would not use chlorine bleach on glass. Conventional glass cleaners often contain ammonia, a caustic chemical that can burn and abrade surfaces—as can chlorine bleach. (Incidentally, never combine the two. They react to release toxic chloramine gas!) Borax is caustic and can scratch, and even white vinegar (or acetic acid), can cause worn spots over time if too strong a solution is used. I recommend no more than ½ cup of vinegar in 1 cup of water, along with a 3 to 4 drops of a green, plant-based liquid soap. Wipe with a soft rag or crumpled newspaper.
- In addition, glass manufacturers advise against cleaning when glass is exposed to heat and direct sun, which can cause cleaning products to cake, build up, and smear. Clean in the cool of the morning or evening; it’s more pleasant for you, too!
- Because your smudge only appears in warm weather, it may be partly caused by a fungus or mold that has settled into the scratches or abrasions in the glass. The best way to get rid of fungi is to ventilate by opening doors and windows and letting sunlight and fresh air in.
- Condensation from your air conditioner may be playing a part; try closing vents in the kitchen and see if that helps.
- Volatile organic compounds (VOCs) offgassing from vinyl surfaces, wall-to-wall carpet, and pressed wood cabinetry glues may be contributing culprits, too. Again, ventilation should help.
Mindy Pennybacker is Whole Living’s “Econundrums” columnist. She regularly answers readers' green-living questions. She is also editor of GreenerPenny.com and author of Do One Green Thing: Saving the Earth Through Simple, Everyday Choices.