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Mold Test Kit Counting Practice

Practice Tutorial on Mold Colony Counting

Basic Terms: For the MoldCheck™ Mold Test Kit Films:

Mold Spores: are too small to be seen. It generally takes three to four days for a mold spore to grow into a mold colony large enough to be seen.

A Mold Colony: first appears as a pencil point dot on the MoldCheck™ film. This is a single colony which has grown from a single spore which settled onto the film. The spore is digesting the food nutrients on the film and growing "vine like" structures called hyphae. The mold colony will continue to grow with a generally circular shape, "fuzzy" edges, a "bulls eye" center, and a variety of colors, such as blue, black, orange, pink and green. Mold colonies produce mold spores ("seeds") which grow like grape clusters at the end of the fuzzy "hairs" called hyphae. Each colony can eventually produce thousands of spores if allowed to grow free.

 

 

Yeast: will first appear on the film as small pencil point sized or slightly larger dot with blue to blue-green to off white color without a "bulls eye" center.

 

 

 

Overlapping Colonies:
Mold colonies tend to grow rapidly after four days and will begin to overlap each other as well as cover the yeast. Two or three colonies will often butt-up against each other. A double cluster will look generally like this:

A triple cluster will look generally like this:

Color Wash-Over

Yeast - if the film has turned all one bluish or bluish-green color, it may be the result of too many yeast colonies to count.

Mold - if the film is quickly covered in black, blue, yellow, orange, dots, and colors, it may have too many mold colonies to count.

When this color wash-over or excessive density growth occurs, the area must be retested for a shorter period of time. Reduce the sampling time to ½ the original time and try again.

Practice Counting:

Count the mold and yeast on these MoldCheck™ films and see if you get the same number (click here for answers). The yeast are shown in blue.

Practice Count 1
___ Mold ___ Yeast (blue)
Practice Count 2
___ Mold ___ Yeast (blue)
Practice Count 2
___ Mold ___ Yeast (blue)
Practice Count 2
___ Mold ___ Yeast (blue)

If there are many mold colonies on a film, it is acceptable to count 1/4 of the film and multiply by four (4) to obtain your total mold spore count.

NOTE: Even professionals will disagree on some counts by a few colonies!

Practice Count 2
___ Mold ___ Yeast (blue)