Healthy Living Spaces


What Looks like Mold but is NOT Mold

While it is impossible to be certain that something is or is not mold without using a microscope, there are some common situations where with high probability what you are looking at is not mold.

Efflorescence

Often the concrete block or brick in crawlspaces and basements have a white, brown, sometimes orange, powdery, crystal-like substance that is mistaken for mold growth. Known as efflorescence, it occurs as water containing salt evaporates from the surface. It may only be an aesthetic concern. It may also indicate a water or moisture intrusion problem which could lead to mold growth and structural damage.


	Not Mold growing.	White crystals on concrete block. Mold growing on the surface of concrete block.

The salts that form crystals may originate from the masonry materials themselves or come from the ground. As water travels through the soil, wall, or building foundation, it dissolves the salts, transporting them to the surface. When the water evaporates, it leaves the salts behind.

To determine if a substance is crystalline, put a few drops of vinegar on the crystals. If the mixture bubbles and dissolves, the substance is minerals; if not it may be mold⁷. Unlike exterior efflorescence, interior salt deposits should be addressed immediately, as they can be signs of ground water intrusion, leaky pipes and defective drains.

Enzyme Staining

Something else commonly observed and thought to be mold is the dark, black staining on wood. There may or may not be active fungal growth associated with these stains. Molds secrete enzymes to break down food into a digestible form. The material may have only been wet long enough for the mold to produce enzymes that stained the wood but not to produce mold spores.

Staining will often remain after the fuzzy mass of mold has been cleaned off by sanding the wood. Mold only puts down roots a few thousandths of an inch into wood. After wood has been lightly sanded or scrubbed clean, the remaining stains are usually not fungal mass but just enzyme stains. It may not look pretty but it’s not hazardous. Enzyme staining can also be caused by bacteria which die as soon as things dry up.

Overheard: “My house smells like stale broccoli - can you come over and tell me if it’s mold?”

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Revised: July 05, 2017.
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