Identifying Molds and Soot

How to tell the difference between mold, soot, moss and efflorescence

Mold is usually easy to identify, but some other types of growth and staining can masquerade as mold. If you've found growth or markings that resemble mold, take time to confirm that they're not actually one of the following mold look-alikes.

Green staining on the outside of the house: If it's the color of plant leaves (chlorophyll green), it's most likely algae or moss and not a concern (except cosmetic, perhaps). However, if you have mushrooms growing on the exterior siding of your house, hire a building investigator pronto! This type of growth will not spread indoors.

Alt=identifying moldsIdentifying Molds and SootA fuzzy white growth on basement walls: It may be mold but is more likely efflorescence, the crystals of mineral deposits left behind when moisture migrates through a foundation wall. To correctly identify it, the efflorescence flakes will dissolve in vinegar or dry up into powder, which mold will not.

Vertical black stripes all over the insides of a home's exterior walls: This is most likely not mold but soot, which deposits on the walls in stripes where framing studs are located, in a flame-like pattern above baseboard convectors, in dots where nails are located, or circular stains on ceilings above light fixtures.

You can test the stain by rubbing it with a little bleach on a paper towel; if the black color remains, it's soot, and if the color goes away, it's mold. Erase soot stains by repainting surfaces, and prevent future staining by avoiding the use of jar candles. These can emit a lot of soot, particularly after the candle has burned down about halfway.