June 12th, 2024

Praxis: Protecting yourself from harmful rays of the sun

By Medicine Hat News on August 11, 2018.

Wow! is all I can say. It has been a real scorcher here in southeastern Alberta the past couple of weeks. I hope that all of you have been practising “sun safety” each time you go outside.

Wearing sunscreen with a strong SPF value is very important as the temperatures rise and those UV rays are more intense.

Hmmm ÉUV rays — what are those, you may ask? Well, you cannot see them, but they are very harmful to our skin and it is believed they can contribute to skin cancer so we need to be aware of them.

I was recently at a local craft store where I saw “UV beads” and it made me think of this activity so you could better understand. Let’s get started!

*Remember to ask an adult before doing this experiment.


– UV beads

– 15 SPF sunscreen

– 25 SPF Sunscreen

– 50 SPF sunscreen

– four plastic zipper bags

– marker for labeling

– sunny location

– measuring spoon

– tray

– location to work inside


1. As you start this experiment make sure you are working inside as once the beads are exposed to light they may begin to change colour and affect the results of your experiment.

2. Using a marker, label the zipper bags with the SPF values and one with “no SPF.”

3. Place 10 beads in each zipper bag and close tightly.

4. Measure one tablespoon of 15 SPF sunscreen and pour it over the beads in the bag.

5. Close the bag tightly and shake it all up so the sunscreen is distributed over all of the beads.

6. Place the bag flatly on a tray.

7. Repeat for the remaining three SPF values.

8. Take the tray outside and place it in the sunlight.

9. Observe.

What is going on?

UV beads have a chemical substance embedded into the plastic that will change colour when exposed to UV radiation (sunlight). The beads will remain white indoors as long as they are kept away from windows or doors where UV light can leak into the room. It’s an amazing way to test the effectiveness of sunscreen or to see if UV light is really blocked out by filters in sunglasses.

There are so many SPF (Sun Protection Factor) numbers available in the stores it is hard to know which one is the best to use. I want to know which SPF lotion really works best at keeping out the sun’s harmful UV rays in order to protect myself when I am outside enjoying the sunny weather. The UV beads are very sensitive to changes in UV energy and you can use them to see which sunscreen blocks these harmful rays. What colours did the beads turn? Are some darker than others? Do the beads change colour over time? The darker the beads, the more UV rays they are absorbing, so likely not very strong at protecting us. Which sunscreen provides the most protection?

If you have an interest in science and want to learn more about Praxis please join us at our AGM Aug. 22 at Paradise Valley Golf Course. The meeting will start at 7 p.m. I hope to see you there.

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. NOTE our NEW address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: praxis@praxismh.ca.

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