I love science experiments, and have always been fond of Petri dish experiments! There’s something satisfying in getting a definite visual result in the Petri dish.

Dan and I decided to try a Petri dish experiment of our own. The toilets in our house needed cleaning, and we wanted to see if there was a difference between the usual cleaner we’ve been using, Lysol Toilet Bowl Cleaner, and the On Guard Cleaner Concentrate. I can’t actually use the Lysol Toilet Bowl Cleaner – it messes with my asthma and gives me migraines. When we clean the toilets with the Lysol, the vent fans have to be on full and we have to open the powder room window. The On Guard Cleaner Concentrate doesn’t mess with my asthma and doesn’t give me migraines, so I was hopeful that it would clean well so that I could actually help with this household chore.

Disclaimer: I did not perform this Petri dish experiment in a perfectly sterile environment or using rigorous study methods. These results are “for fun” and should not be mistaken with a proper scientific study.

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The Experiment

First, we flushed each toilet to be sure they were clear of any debris. Then I took a clean swab, and swabbed around the bowl and up under the rim. Each toilet got its own swab and own “before” Petri dish. Be sure you label all of your Petri dishes with location swabbed and if it was swabbed before or after cleaning.

Then, we cleaned the master bathroom toilet using the Lysol Toilet Bowl Cleaner according to the instructions for disinfecting: coat bowl with cleaner, let it sit for 10 minutes, scrub, flush. We flushed a second time to make sure the cleaner was out of the bowl. I then used a clean swab to swab around the bowl and under the rim again, and put that sample into a new Petri dish.

Since we have one toilet brush, Dan rinsed the brush thoroughly in the tub between toilets to prevent as much cross-contamination as possible.

The On Guard Cleaner Concentrate has different formulas on the bottle based on useage. Since we would be cleaning in the bathroom, we used that formula: 3 tablespoons of the cleaner concentrate in 24 ounces of water. Well, since my spray bottle is an 8 ounce bottle, we sized it down to 1 tablespoon in 8 ounces of water. There aren’t specific “this is how you disinfect” instructions on the bottle, so we decided to use the same process as the Lysol: coat bowl with cleaner, let it sit for 10 minutes, scrub, flush. After a second flush to clear the bowl of cleaner, I again swabbed around the bowl and under the rim.

Then, you place the Petri dishes upside down in a warm location where they will be undisturbed for up to three days. Since we don’t have central air conditioning, and it’s summer now, the master bathroom was warm enough to incubate the dishes (and that shower is broken right now, so we could sit them on the edge of the tub and they wouldn’t be in the way).

We let the Petri dishes sit for about three days, then took photos. To properly dispose of the dishes, you seal them in a Ziploc and throw them out.

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What do you think of the results? I know Dan saw them and said “well, it’s pretty obvious the master bathroom toilet needs to be cleaned again!” I’m excited that the On Guard Cleaning Concentrate is an effective cleaner that does not cause me to get migraines nor cause breathing problems for me!

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