Why?

One day when I was done showering and I was cleaning the little grate/filter of hair, I thought to myself if hair would be effective at filtering. I had read somewhere that hair have small pores/holes that can trap small particles like pollen, so why not other particles too?

Hypothesis:

If we add a layer of hair to a filtration process the amount of small particles and bacteria will decrease, as a result of getting stuck in the hairs cuticles.

The Experiment:

Step 1 (Agar filling and preparation):

The first thing I did was to make and fill my potato dextrose agar, which I used to test microbe growth after filtering a microbe solution. Firstly I weighed out the appropriate amount of powder for two Petri plates. Then I added 20mL of water into a small pot together with the potato dextrose powder and heated and stirred it for 30 seconds. Then I poured the now fluid agar into my two Petri plates and let them sit until the agar solidified.

Step 2 (Getting the hair ready):

After cleaning the shower grate I put the hair in a bowl and washed it in 70% alcohol just to kill the already existing microbes, but not enough to denature the proteins in the hair. Together with the alcohol bath I put it out in the sun so the microbes could die from the heat and radiation too.

Clean hair in alcohol and sunlight

Step 3 (Getting microbes):

To make sure that the hair would come up against a variety of different microbes I went around in my house to find as many different bacteria as I could, which included bacteria on my scalp, bacteria from old cheese, and bacteria from a variety of doorknobs/handles.
The solution ended up looking like this:

Step 4 (The filtering process):

When it came to the actual filtering I wanted to test the hair as the filter, but I also chose to include a tea filter to see if the hair would perform better or worse. I put exactly the same amount of microbe solution in both filters and let the fluid come out on the other side into two different cups.

Step 5 (Petri Plate and wait):

Now that I had the filtered liquid from both filters as well as the unfiltered solution it was time to drop the solution in the Petri plates. I marked each Petri plate with a negative and a positive side, where positive meant that side had been filtered, and the negative side was the unfiltered control. Each Petri plate got three drops of liquid per side, so a total of six drops per Petri plate. Then I set them aside for three days for the microbes to grow.

F stands for filter AND H stands for hair

Results:

After three days I finally got the results, and they were definitely not in support of my original hypothesis, which I was also increasing doubting the further I went into the experiment.
In the picture below, the left side of H is the positive side, and for F it is the left side that is positive, i.e. the negative control sides are the ones in the middle.
The hair did seem to decrease the growth of microbes slightly, but well within the margin of error. So I see this experiment as a possible correlation, but not one fit for an At-Home lab to find.

Possible Source of Error:

I should have taken picture every day, or maybe even every morning and every evening, to more closely follow the progression of the growth, as only monitoring the third day, might have caused the microbes to just have too much time to grow, so the results aren’t as clear.
I might also have rushed the cleaning step too fast, as it is still possible that some microbes might have gone with the hair into the solution.
The last possible error could be the amount of hair I used as a filter. The tea filter was big and covered a big area, whereas the hair was not as densely packed as the tea filter.

Conclusion:

Thank you for reading through this experiment, and I hope that you learned a little bit about hair proteins and the filter effectiveness. Although the results remain inconclusive in my view, I will follow this experiment up, when I eventually have access to a better lab and materials. As always if you have any questions or suggestions feel free to comment on this article below.

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