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Foldscope In The Classroom: Spring Cleaning


Is spring cleaning good for your health?

Before we attempt to answer the question above, let’s answer this one: What is dust? Dust is made of material like pollen, dirt, insect parts, hair, dust mites, and skin cells. Wind carries these dust particles from place to place and eventually deposits them on indoor surfaces.

How concerned should we be about dust and how important is spring cleaning to our health? Let’s try to answer these questions with our Foldscopes!

Dust inside of a windowsill
Figure 1. Dust inside of a windowsill
(Photo Credit: Holly A. Stuart)


Spring cleaning is actually a tradition that began in the East with Jewish, Iranian, and Chinese cultures. The arrival of spring involved rituals, some religious and some secular, to ensure that the home was clean enough for the new season and year. As temperatures rose and days grew longer, people prepared their homes for the warmer season ahead by opening windows, and airing out rugs and furniture, helping to shake off the cold dark winter nights.

In the late 1800’s scientists began recognizing that germs (microscopic bacteria, fungi, and viruses) were responsible for diseases like anthrax, tuberculosis, and cholera. Because these germs are invisible and on surfaces everywhere, there became an association between cleanliness and improved health. This gave rise to a rebranding of spring cleaning in the US as National Clean Up Week in 1917 that was tied to a large marketing campaign for household disinfectants.

This activity will allow you to investigate (1) if there are indoor spaces where bacteria growth is more likely to occur and (2) what the bacteria could have been consuming in that location.

A petri dish showing colonies of growth on nutrient agar
Figure 2. A petri dish showing colonies of growth on nutrient agar
(Photo Credit: Holly A. Stuart)


Nutrient agar is a medium that is used by scientists to study bacteria, fungi, and mold. It is a food source for these microbes and encourages rapid growth of colonies that can be seen by the naked eye. Therefore, if you see anything growing on your petri dish, it is evidence that those microbes were present on the surface swabbed with your cotton swab (you just provided them with the nutrients they needed to reproduce quicker than the surface they were on).

Here is what you will need and what you will do in order to complete the activity with your students.

  • Procedure:
  1. Place a piece of tape, sticky side down, on a dusty surface.
  2. Pick up the dusty tape and place it on a slide.
  3. Place the slide into the Foldscope and observe what is in the dust.
  4. Using your science notebook and pen, draw and label what you saw in your Foldscope.
  5. Take a sterile cotton swab, rub it over the dusty surface
  6. Using a zig zag motion, rub the dusty swab over the nutrient agar inside the petri dish.
  7. Cover the petri dish (make sure to label it with the date, time, and location where the sample was collected), seal it shut with tape, and sit it upside down in a warm dark place for a few days.
  8. Repeat the above procedure for a freshly cleaned surface.
  9. After a few days of incubation, check the petri dishes for growth.
  10. Keep the lid on and use the Foldscope LED Magnifier to observe the colonies that are growing in your dish.
  • It is important to remember that the petri dishes should not be opened once colonies of bacteria and mold have begun growing on the agar. When the observations are complete, the sealed petri dishes should be disposed of by throwing them into the trash.
  • Using your science notebook and pen, draw and label what you saw in the petri dish.

Were there sample locations that produced more colonies than others? Why do you think that is?

Dust viewed through a Foldscope at 140X magnification plus 5X zoom on phone
Figure 3. Dust viewed through a Foldscope at 140X magnification plus 5X zoom on phone
(Photo Credit: Holly A. Stuart)

Do you think that all methods of cleaning would give the same results? Can you design an experiment to test your hypothesis?

Real World Scientist:

Felipe Soberón is the chief technology officer of WellAir, a company that specializes in air purification products. Soberón was born in Lima, Peru. In 2005 he received his PhD in plasma physics from the National Centre for Plasma Science and Technology at Dublin City University. He was always interested in math and physics, so it came as no surprise to his family that he earned a degree in physics after high school. Soberón grew up in an area with high levels of air pollution which negatively affected his respiratory health. As a result, issues related to air quality became important to him. His personal story pushes him to work hard creating solutions that make indoor air healthier year round, not only when spring cleaning occurs. How could your observations contribute to Soberón’s research?

Real World Scientists & Artists:

Every year since 2015 the American Society for Microbiology has held an Agar Art contest. The themes change annually and serve to inspire scientists to channel their inner artists. It is a great way to demonstrate the powerful relationship between science and art. To create agar art, scientists use different types of agar and cultures to create amazing works of art that rival traditional paintings found in museums! Did anything in your petri dishes look like a work of art?


This blog ties together the three dimensional framework of the NGSS. It covers the Disciplinary Core Idea of Life Science. Students will see the Crosscutting Concept of Energy and Matter. This activity is also a way for students to deepen their understanding of the Science and Engineering Practice of Plan and Carry Out Investigations.

NGSS tie ins

However, this exploratory activity can go beyond the science classroom. Join forces with:

  • a Social Studies teacher to investigate the spring cleaning practices in different regions, how they have changed over time, and how they impacted history,
  • a Math teacher to create graphic representations of bacterial growth in the petri dishes over time,
  • an ELA teacher to create a PSA about spring cleaning,
  • and an art teacher to create agar art!
Dust viewed through a Foldscope  at 140X magnification plus 5X zoom on phone
Figure 4. Dust viewed through a Foldscope  at 140X magnification plus 5X zoom on phone
(Photo Credit: Holly A. Stuart)


Make sure to share your observations, hypothesis, results, and interdisciplinary extension activities. Submitting your Foldscope images of dust and pictures of petri dish colonies to the Microcosmos will help build up a strong scientific database that can help support new and innovative scientific research!