Do masks block germs?

3/4/2021

Answer: YES! 

I am very surprised by these results. I'm also a little disappointed. I wanted to find masks useless so we could stop wearing them.

Procedure

This was my daughter Katie's 7th grade science fair project. She tested how well disposable and cotton masks catch bacteria when someone is coughing and talking. Even though this was my daughter's project, I was there the entire time helping and supervising so I know the results are accurate. For the full procedure and pictures of all of the results, please read the PDF of her science fair report attached to the bottom of the page. Basically everyone in the family coughed, talked, and sang into agar plates for 1 minute with and without wearing masks. We repeated it many times. The cotton masks were boiled for 5 minutes and allowed to air dry between tests. New disposable masks were used each time. 

Results

For the full results and discussion, please read Katie's science fair report PDF which is attached to this page. Both the 3-ply disposable masks and the white 2-ply cotton mask did a great job containing bacteria. Yes, viruses are smaller than bacteria. However, the pores in the masks (at least the cotton mask) are bigger than most bacteria, yet they still caught it. This gives us hope that the Covid-19 virus may be caught in the masks as well. You can also watch her presenting her poster here on YouTube. 

*My take: I have spent the last 10 years begging people to stay home when they are sick, to keep sick kids home from school when they are sick, to stay out of nursing homes if you have even recently been sick, and to stay out of work in food service if you have recently been sick. I've preached the importance of washing hands when you get home, before eating, before handling food, after going to the bathroom, after changing diapers, etc. I firmly believe that those are still the most important things to do. These experiments show that masks block germs (at least bacteria). So mask wearing may be helping less people get covid during this pandemic. However, you can see that masks get germy fast!  It is certainly possible that wearing a moist bacteria-laden mask all day could be bad for your health. So be sure you are wearing a CLEAN mask. Please read my experiments on how to clean your mask. I look forward to the day when we don't have to wear masks at all. However, everyone should still follow my "stay home when you are sick" and "wash your hands" rules forever. 

Face Shield Experiments

After Katie's science fair project was done, I couldn't resist testing face shields. Anyone with a shred of common sense knows that germs can go under and around face shields. I decided to test it anyway. The face shield is almost invisible in this photo of my son doing the experiment.

I had my son Jon wear a face shield and cough, talk, and sing for 1 minute holding an agar plate underneath the shield as shown in the above photo. He also coughed, talked, and sang with an agar plate about 4 inches in front of their face with no face shield. As a negative control, they held a plate under the shield for 1 minute without coughing or talking. 

Results

Coughing, talking, and singing with no mask or shield

Coughing, talking, and singing while wearing face shield.

Negative control-holding plate below shield for 1 minute with no coughing, talking or singing

I also swabbed the inside of the face shield both before and after the coughing, talking, and singing. I rubbed the swabs onto agar plates.

Clean Face Shield Before 

Face shield after coughing, talking, and singing for 1 minute

I had my son Michael do this experiment as well.

As you can see, lots of bacteria did get stuck on the inside of the face shield. But a lot of germs also escaped underneath. I don't personally feel that wearing just a face shield is good enough to protect other people if you have Covid-19.

I personally wear the blue disposable face masks. I find them the most comfortable and the easiest to breath in. I could not see the pores in the blue disposable masks using a magnifying loupe. I could see the pores in cotton masks.