At the start of the school year we were lacking for science projects to do. There was one thing we had a ton of — masks: bandanas, cotton masks, synthetic, surgical masks… We also had a cheap little microscope, bought by my mom years ago for my son, used once or maybe nonce. We were settled on the couch with our laptops, when we thought: “nope, today we’re rolling up our sleeves!” Even though it was entirely spontaneous with no prep, the lab turned out unexpectedly nicely. Disclaimer: water is a weird liquid and the permeability of a material to water maybe doesn’t have anything to do with how well it protects against COVID-19 transmission, so no conclusions there. Coincidentally, the things that real studies show are better at preventing COVID-19 spread tend to look less porous, and also let less water through. And permeability and fabric under the microscope is what this lab is about.

Materials and equipment needed:

  • Microscope
  • Stopwatch or timer
  • Measuring cup (ideally 2)
  • Masks & bandana + any other face coverings

Observation and measurement:

  • Place mask or bandana under microscope at 40x magnification, make observations (e.g. what do the fibers/weave look like, is there light coming through? etc.)
  • Measure out a quantity of water (1/2 cup or 1 cup, so ~250mL or 500mL)
  • Place mask or bandana over second cup (nice if this one is a measuring cup too, but you can also pour out the liquid to measure).
  • Pour the water you measured into the second cup
    • Use a stopwatch to time how long it takes for most of the water to seep through
    • Read off how much liquid has made it through (the rest could e.g. be absorbed by the fabric of the face covering)

That’s pretty much it. We had such a good time with this one, that we also repeated it with one of my son’s friends (it was a warm September day, we did the lab outside, everyone wore masks etc.). It’s good to have at least two kids working on this together, so that one can work the timer while the other is pouring, or hold the mask so that it doesn’t fall into the cup etc. On that occasion I spent 5 minutes creating a lab sheet they could fill out, I’m sure you could make a much better one…

OK, so first thing, fabric looks really cool under the microscope!  This alone should have your kid going “Wow!” We found lower magnification (40x) to be more interesting than 100x because you see more of the weave.

The above image is from a bandana I wore as face covering for the first few months of COVID, here placed under the microscope.

The bandana is so permeable that the water will go right through, leaving the kids scrambling to start/stop the timer at an appropriate time. If you have a range of face coverings, they should be different enough that precise timing is not of the essence, but having a highly porous fabric in the mix adds to the excitement.

On the other end of the spectrum are surgical masks. Ours didn’t let any water through in any reasonable amount of time and this should have your kids scratching your heads in surprise, so I recommend doing this one last, as we did by accident. This also lets the kids get creative about how they’d like to write this result in their notes.

Our cheap little microscope had the option of illuminating either from above or below. The “from above” illumination was nice for seeing the color and structure. The from below was great for seeing where the light got through and where there were holes. For a green neck gaiter, here is the contrast:

On the other end of the spectrum, the surgical mask has a very different structure, and when illuminated from below, you don’t see clear pockets of light, rather there is diffuse light that is coming through additional layers.

That’s about it. If you happen to have a microscope collecting dust somewhere (it’s under a dust covering through, right?), I highly recommend this quick activity. If you do do this lab, I’m curious what you found and how you enhanced it.

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