Adventures in Wonderlab

Adventures in Wonderlab

Fun science adventures for all ages!

What is the Germiest Thing in your Home?

So, what is the most germ-filled item in your home? Any guesses? The toilet? The floor? Your children (ha!)? Believe it or not, the germiest thing in your home is the kitchen sponge. That’s right! That sponge you use to “clean” your dishes.

Despite what might seem obvious, scientists have proven that kitchens actually have more bacteria than bathrooms. This was mainly due to the kitchen sponge, which contain the most bacteria in the whole house.

So, what should we do with this disgusting information?

For me, about a year ago, I ditched sponges in exchange for Peachy Clean silicone scrubbers. I did not know the exact science behind how germy kitchen sponges are… but I did know that my sponges started to stink after about a week of use.

How do silicone scrubbers compare to sponges?

With the news about how bacteria-filled our kitchen sponges are, I began to wonder how my Peachy Clean silicone scrubber would stand up to the sponge. Sure, there was no odor or visible mold on my scrubbers, but how much bacteria might be growing there?

It was time for me to get out my trusty agar plates again for another science experiment! (I have also used the agar plates to do a hand washing experiment, and a shopping cart study!)


Agar Plates and Growing Bacteria

I purchased some luria broth agar plates, which are used to grow environmental bacteria, including E. coli. Other types of agar plates are used to grow pathogenic bacteria- I did not want to grow any of those in our home! I should also note here that only bacteria can be grown on agar plates – no viruses.

Petri dishes

Heating lamp and thermometer on the left (for our incubator), and agar plates are stacked on the right.


When it is time to grow the bacteria, I placed the agar plates in an upside-down position in a homemade incubator with a temperature between 85 and 100 degrees F. For the homemade incubator, I used a plastic bin, a thermometer, and a heating light bulb as a heat source.

Homemade incubator

Growing bacteria

After 1-2 days in the incubator, I watched for the appearance of small bacterial colonies (usually white or yellow dots) on the surface of the agar plates. You need millions of bacteria in one spot just to see one dot on the agar plate.

My Sampling Method

I purchased new Scotch Brite sponges and Peachy Clean silicone scrubbers. I used them both for dish washing over a one-week period. They were both stored in a sponge holder attached to the side of my sink to drip dry when they were not in use. I took samples after 2 days, 5 days, and 7 days of use. I took samples in the morning, after the sponge and scrubber had been drying overnight in my sink holder. To take the samples, I pressed the corner of the sponge/scrubber into the agar plate.

New sponge and silicone scrubber

Peachy Clean silicone scrubber on the left, and Scotch Brite sponge on the right.


Day 2

After 2 days of dish-washing, I took my first samples. I pressed the corner of the sponge on the top section of the agar plate, and the Peachy Clean silicone scrubber on the bottom section of the plate. Due to the rough texture of the Peachy Clean silicone scrubber, I accidentally pressed too hard and broke through the agar – hence the speckled appearance on the plate. There were over 100 colonies of bacteria grown from the sponge sample, and only about 10 colonies from the Peachy Clean silicone scrubber.

Day 2: Sponge vs. Silicone Scrubber

Day 2 Results: Sponge sample on top, silicone scrubber sample on the bottom. Bacterial colonies circled in pink.

Day 5

After 5 days of dish washing, I took another sample. This time, I was careful not to press the silicone scrubber too hard into the agar plate. The sponge sample grew so many bacteria, that I was unable to count how many colonies I grew (A LOT!). The silicone scrubber sample grew about 25 colonies.

Day 5: Sponge vs. Silicone Scrubber

Day 5 Results: Sponge sample on top, silicone scrubber sample on the bottom. Silicone scrubber bacterial colonies circled in pink.

Day 7

After a full week of dish washing, I took my final sample. Again, the sponge sample grew so many bacteria, that I was unable to quantify how many colonies I grew. And for the silicone scrubber sample, I was only able to grow 1 colony of bacteria.

Day 7: Sponge vs. Silicone Scrubber

Day 7 Results: Sponge sample on top, silicone scrubber sample on the bottom. Silicone scrubber bacterial colony circled in pink.


I am sticking with my Peachy Clean silicone scrubbers! I think the result pictures speak for themselves. In addition, after a week of dish washing, the sponge had a bad odor, as compared to the Peachy Clean silicone scrubber which still had a fresh peachy smell.

If you’d like to give the silicone scrubbers a try, click the picture below.

Click on the picture to view on Amazon.

Happy New Year, everyone – Keep it clean!

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