The Effectiveness of Washing Hands

Purpose: The purpose of this experiment is to test the effectiveness of washing and drying hands on the number of bacteria on the hands. This experiment will basically test whether bacteria are better cleaned using soap, drying with paper towels, air drying, or using chemicals like hydrogen peroxide or alcohol

Hypothesis: It is the hypothesis of this experiment that bacteria will be best cleaned off when they are washed with chemicals like soap or hydrogen peroxide and the hands are then drying on a sanitary object like clean paper towels.

Equipment:  Used in this experiment was Dirt (as a source of bacteria) Soap, Hydrogen peroxide, alcohol, Paper towels, bath towels, 2 agar plates, an incubator, a pen and paper.

Procedure: The first step is to divide each agar plate into 8 sections and number them 1-16. On sections 1-4 place hands in dirt. The place left thumb on section 1 and again on section 2. Place the right thumb once down on section 3 and then clean with the Alcohol and place on section 4. repeat in a similar manner for sections 5-8 and on the 8th section use Hydrogen peroxide. For sections 9-12, place dirt on thumb and wash hands without using soap. On section 9, air dry the thumb before placing. Section 10 dry on paper towels, on section 11 use the bath towel and section 12 dry hands on pants. Use similar drying techniques for sections 13-16 however, this time use soap while washing hands. Record the relative growth on each section between 1-5 (5 being most growth) after 5 days of incubation.


       Bacteria Rated as * Low Bacteria - -- -- -- - -- --*****High Bacteria
Section #
What was Done
Relative amount of Bacteria
1 Dirty Thumb Pressed once (Left Thumb) * * * * *
2 Dirty Thumb Pressed Twice (left thumb) * * *
3 Dirty Thumb Pressed once (Right Thumb) * * * * *
4 Dirty Thumb cleaned with Rubbing Alcohol (right thumb) * * 
5 Dirty Thumb Pressed once (left Thumb) * * * 
6 Dirty thumb pressed Twice (left Thumb) * * *
7 Dirty Thumb Pressed once (right thumb) * * * *
8 Dirty Thumb Cleaned with Hydrogen Peroxide
9 Washed (no Soap) Air dried * * * *
10 Washed (no Soap) Paper Towel dried * * 
11 Washed (no Soap) Bath Towel dried * * 
12 Washed (no Soap) hands dried on pants * * * *
13 Washed (with Soap) air dried * * * 
14 Washed (with Soap) Dried with paper towels
15 Washed (with Soap) dried with Bath towel
16 Washed (with Soap) dried on pants * * * 

Conclusion: The results reveal many things about the effectiveness of drying hands. In general it looks as though the use of soap is good at cutting down the bacterial levels, however more important it seems is to dry hands on either a paper towel or a bath towel as it tends to cut the bacteria drastically as opposed to letting your hands dry on either a hand blower or just wiping them on clothing. It should also be noted that the chemicals Hydrogen peroxide and alcohol were pretty efficient at cleaning the bacteria off dirty hands. Other things that should be noted is that washing hands with no soap and then drying them on pants produced almost the same amount of bacteria as not washing hands at all!

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Scientific AmeriKen