What Does Toxic Black Mold Look Like in a Petri Dish or Home Mold Test Kit?
Please note in this article we are discussing the appearance of Toxic Black Mold in petri dishes or in home mold test kits. This mold is also known as Toxic Mold, Black Mold, or Stachybotrys.
For a discussion on what it looks like on walls in a water damaged home click here. And see photos of toxic mold provided by our mold inspection company.
Toxic Black Molds Appearance in A Petri Dish
Above is a picture of three separate colonies of toxic black mold in a petri dish. The three colonies of toxic mold in the photo started out fibrous and white like circular patches of cotton.
Next, they started to turn black in the centers. In this image you can see the black centers.
The black centers might have a hint of greenish, or grey. If you look closely and have good color vision yon can see the black, greenish, and white in the centers of the colonies.
The black centers will both darken and expand to eventually cover the entire colonies surfaces till the mold is all dark black from center to edge.
Photo of actual toxic mold in a petri dish.
Above is a photo showing what mature toxic black mold looks like growing in a petri dish. No more green or white, just black. In this image the lab is using a square sheet of paper as a food source. In most dishes the mold will appear rounder because most dishes do not use square paper.
Clarification
So why is a mold we call toxic black mold sometimes fuzzy and white like cotton with colors like greenish, or gray?
The reason is because this is how the mold will appear in the petri dish when it is still young and only forming light colored microscopic fibers called mycelium.
The reason for the color change is that the young mold fibers start out white. After some time, the young white fuzzy mold fibers will mature and start to form black spores. The black spores is that gives the mold it’s black color.
You will not see the tiny black spores with your necked eye, but when thousands or millions of dark black mold spores have formed on the mold in the test kit, they will cumulatively give the mold it’s characteristic black appearance.
The color change to black will start in the center and spread slowly to the edges. The reason is because the center is older, so the center produces spores first.
Photo of toxic mold spores under the microscope.
Problems with Petri Dish Test Kits.
Do Not Let a Mold Remediator rip your house apart looking for toxic mold because you saw something like the above black fungus in a petri dish sample of your homes air.
Further Analysis Needed
Several other common black molds can be found in your homes air. Many of these black colored molds will show up in your petri dish test kit almost every time. It can be difficult to tell them all apart without the help of a lab.
Spore Counts Not Possible
These petri dishes do not properly measure spore numbers.
You will not know if you have a lot of spores, or a normal expected number of spores in your air. As you can imagine this is a major drawback.
Growth Rate Issues
Toxic black mold is known for growing slower than many other very common household molds like Pen Asp and Mucor. Sometimes a problem that labs run into is that fast growing molds will fill the home mold test kit up before toxic black mold has a chance to grow in the test kit dish.
So, while some toxic black mold spores may settle in your home test kit you may not see the actual mold growth because it very often gets crowded out by faster growing molds. This is just one of the reasons why home mold test kits may be very popular among homeowners, and fun to use and observe, but not as effective as some newer alternatives.
Wrong Media Type for Toxic Black Mold
Another limitation of home mold test kit’s is that they may not be suited to grow toxic black mold at all. Stachybotrys mold will sometimes successfully grow in typical mold test kits but will more often grow in a petri dish with specialty agar media (mold food). Stachybotrys prefers high cellulose and low nitrogen content foods like PDR agar or plain wet paper.
Traditional mold test kit. Pro Lab is a popular mold lab among mold inspectors. They are also a leading seller of petri dish style mold test kits. You can buy the kit here. See the colonies yourself, or for an extra fee have them identified by the lab. The growth is interesting but the numerical data on how much mold you actually have in your air will be extremely limited. And toxic mold may not have a chance to grow due to being outcompeted on a media not formulated to that specific species of mold.
A New and Improved Home Mold Test Kit on the Market
Petri dish style home mold test kits are not as effective as something like this newer more scientific home mold test kit sold here.
This newer test kit is similar to what mold inspectors like myself use. It allows a lab analyst to do a direct examination of the actual mold spores.
There is no chance of fast-growing spores crowding out slower growing spores like Stachybotrys.
You will know the actual number of spores in your air.
You will get a much more accurate picture of all types of spores in your air.
A new and improved home mold test kit being sold online here. It lets you know how many spores are in the air that it samples. Analysis of results is more accurate than what dishes provides. But as is the case with petri dishes, this kit also required an additional lab fee.
Mold Inspections
No home mold test kit can compete with a true mold inspection by a licensed and certified mold inspector. A mold inspector is more expensive but he or she will take samples using a spore trap and pump similar in many ways to the one above. Such pumps allow for direct examination of the spores under the microscope regardless of growth rate. Most importantly he or she should look for your mold problems source, and hopefully find it’s causes, and make recommendations bases on years of experience. You do not get these services with any test kit.
About the Term Toxic Mold
In my personal experience most molds seem to cause many of the same health problems, allergy and asthma, regardless of the toxicity of the mold. So, don’t let the name toxic mold throw you into a panic. Talk with your doctor if you want advice on mold and what it can do to you.
In my opinion as an inspector, toxic mold does not mean immediate and imminent poisoning of you and your family. It means you have water damage in your home. This mold loves to grow after building materials have become very wet for a prolonged period of time. If black mold is in your homes air then you likely have a serious mold and water damage problem.
Curious about what it looks like in a home? Check the below image out. or Click here.
Close up of Toxic Black Mold on a wall in West Palm Beach Florida.
References:
Field Guide for the Determination of Biological Contaminates in Environmental Samples.
An AIHA Biosafty Guide
American Industrial Hygiene Association
1996
Identifying Filamentous Fungi A Clinical Laboratory Handbook by Guy St-Germaine and Richard Summerbell.
Star Publishing Company 1996.
Page 196
For information on what toxic mold looks like in the home click her