If I put different sun-blocking materials in front of UV sensitive beads then the sunscreens will do the best at blocking UV light because sunscreens have chemicals like Octocrylene and Avobenzone that block UV exposure.

Ultraviolet light

Johann Wilhelm discovered UV light in 1801, when he put a prism in front of a piece of photographic paper, and below the purple in the rainbow, was a black strip.  This was from exposure to UV light which humans cannot see with their naked eyes.  Some examples of where you can find UV light are: the sun, tanning beds, screens, and some flashlights. 

Ultraviolet light (UV light) is not visible, and is in the wavelength of 10-400 nm.  It has a higher density than normal visible light which is in the wavelengths of 400 - 750 nm (see the diagram on the next slide).

There are 3 types of UV-UVA, UVB, and UVC. UVC is the most dangerous but is blocked by our Earth’s protective ozone layer. Radiation from UVA is less intense but has a larger radiation reach, UVB is more intense and harmful to us. UVC is the most harmful but has the shortest distance it can travel.

 

The harmful effects of UV rays on people

According to the Canadian Skin Cancer Foundation over 80,000 people get diagnosed with skin cancer in Canada each year. Skin cancer is caused by too much time in the sun, causing burns and harming your DNA. Some ways to prevent skin cancer is to limit your time outside and to wear sunscreen. Eye cancer can be formed by too much exposure to UV light. Some signs of eye cancer are blurry vision and dark-like vision.  

 

Human skin has an epidermis, which is the outside of your skin and the dermis, the layer beneath.  UVA can damage the epidermis and UVB penetrates the dermis (see the diagram on the next page). UV light does this by burning the skin. Some effects of too much exposure to UV light are skin cancer, eye disease, and sunburn. 

 

UV light kills our skin cells by having much more energy than visible light or in other words burning our skin alive!  Human skin is protected from UV light by our clothing, sunscreen, and natural pigment.

 

Sunscreens

In 1938, a swiss student named Franz Greiter was inspired to make sunscreen when he was sunburned hiking in the alps. After experimenting with a few prototypes, Franz Greiter made Glacier Cream. This was the first modern-day sunscreen. 

 

SPF on sunscreen means sun protection factor. The stronger SPF is, the longer your skin will be protected.  Also the stronger SPF is, the better protection you will have from UVB light.   

There are two types of sunscreens on the shop shelves today:

 

1. Chemical:  The ingredients in chemical sunscreens absorb UV light like a sponge.  

 

• Avobenzone Homosalate - A recent study shows that this may be toxic
• Octinoxate - Organic, specifically absorbs UVB rays
• Octocrylene - Water resistant can boost chemicals like avobenzone
• Benzophenone-4 - Was recently banned and can be allergic to some skin types
• Ensulizole Octyl - Oil soluble, commonly used in moisturisers, specifically absorbs UVB rays
• Methoxycinnamate - Organic, The most common UVB filter in sunscreens and cosmetics. Has health side-effects.
• Padimate O - Damages DNA, Organic and water-soluble

2. Physical:  Ingredients (Titanium dioxide, Zinc oxide,) that protect you like a shield - these are the   best  sunscreens to protect your skin from UV rays.

 

Different fabric types

All of my Fabrics used throughout this experiment used the twill weave. However some fabrics were woven tighter than others, for example rayon was woven tighter then silk. Rayon is also more dense than a lot of other fabrics. Cotton has natural lignins that prevent UV light. Rayon, Cotton and silk are supposedly the best fabric to prevent UV light.

 

UV beads 

UV beads are beads that change colour when exposed to UV light; the darker they get, the more UV light they have been exposed to. UV beads have a chemical inside them that changes color when they're exposed to UV radiation called spiro compounds.  Spiro compounds are used because it’s really good at detecting UV light and reacting to it. 

 

My experiment used UV beads to determine when UV light is present and to help measure exposure. 

 

 

Manipulated:

The sun protecting material that is blocking the UV beads. 

 

Responding:

The darkness of the UV beads

Controlled:

• Amount of UV beads 
• Amount of UV light shined on  the material 
• The color of the fabric
• Distance to the UV light
• Time of exposure to the UV light
• Amount of sunscreen

Materials

• A package of UV beads
• A plank of wood and  a sheet of plastic (same size)
• 9 jar lids  (6.35cm)
• Four types of fabric and two types of sunscreen
• Tin foil and SaranWrap
• Sunglasses
• 2 ½ inch drill bit and a drill 
• A room where you can do your experiment
• Nine screws and a screwdriver
• A tanning bed or a UV flashlight

 

Procedure

1. Place equal amounts of UV beads in test jar lids that are secured to a piece of wood 
2. Using a plastic sheet, make holes that align with the UV jar lids on the wood
3. Put test materials / sunscreens (applied on SaranWrap) over the holes - leave an open hole that will be fully exposed for the control variable
4. Align the test materials over the jar lids
5. Place the experiment on a tanning bed and then turn it on for 15 seconds
6. Record the results by removing the plastic sheet and taking a photo

Take the photo of the individual test materials and analyze the results using a colour-finder app and the darkness measurement(I used https://devpicker.com/image-average-color )

 

Observations:

These are the photos I put in the color avrager to analyze the results:

Test	Silk	Rayon	Cotton	Tinfoil	Control	Nylon	SPF 4	Sun glasses	SPF 50
Test 1
Test 2
Test 3

 

Qualitative Observations

Sik	Rayon	Cotton	Tinfoil	Control	Nylon	SPF 4	Sun glasses	SPF 50
My silk sample was very thin.  The sample was also white in colour.  This sample was  not a very good UV blocker.	My rayon fabric was very thick. Also the sample was white. The rayon sample was a great UV blocker.	My cotton sample was very thin and see- through. The sample was also white.	My tin foil sample was completely reflective. Tin foil completely blocked UV light.	My control sample was fully exposed to UV light.	My nylon sample was very thin, almost see- through. Also the  sample was white. This sample was  not a very good UV blocker.	My SPF 4 sample sprayed on clear SaranWrap. Although it smelled nice, it was a very poor UV blocker.	The sunglasses I used were relatively cheap but said it was UV protection coated. Although it was solid, you can see through it.	My SPF 50 sample sprayed on clear SaranWrap. It did not smell as nice as the SPF4 but it was a very good UV blocker.

 

Quantitative Observations - these are the results from the colour averager:

	First	Second	Third	Average	Median
Silk	15%	25%	16%	19%	16%
Rayon	30%	44%	38%	37%	38%
Cotton	14%	30%	18%	21%	18%
Tinfoil	36%	46%	39%	40%	39%
Control	11%	11%	11%	11%	11%
Nylon	13%	28%	13%	18%	13%
SPF4	15%	22%	12%	16%	15%
Sunglasses	27%	39%	35%	34%	35%
SPF50	27%	39%	34%	33%	34%

 

Below is the reults represented graphically:

In my experiment the manipulated variable is the sun blocking materials including SPF 50 sunscreen, SPF 4 sunscreen, and different fabrics. The responding variable is the darkness of the UV beads after I shined UV light on the sun blocking materials. By changing the sun blocking materials, I am testing how much UV light goes through it.

 

The natural fabrics (silk and cotton) had about the same results - approximately 20% brightness.

 

Synthetic fabrics (nylon and rayon) had very different results - nylon had a 18% brightness with rayon being far better at 37%. Tinfoil (the only metal) performed the best at blocking UV light with a brightness of 40%. The UV protection coated sunglasses were effective at blocking UV light and had a 34% average brightness.  

 

SPF sunscreens performed differently. SPF 50 (Neutrogena) was effective at blocking UV light at 35% brightness. The SPF 4 sunscreen I tested was a Hawaiian Tropic brand and had the worst performing UV blocking average brightness of 16%.

I learned that different sun blocking materials block UV light differently. When I go outside on a day that has a high UV index, I will wear fabrics that are tightly woven and thicker.  For exposed skin I will wear high SPF sunscreen and also I will wear sunglasses to protect my eyes.

 

Some fabrics block UV rays better than others primarily due to the thickness and weave of the fabrics. The type of fabric matters as well, the silk and nylon samples are the same thickness and performed differently. This is consistent with the findings in my background research. For this experiment I focused on the type of material and used only white coloured fabrics.  Darker colours may have absorbed UV light better, for example the sunglasses on average performed better than any fabric or sunscreen on average. The sunscreens used in this experiment work using chemical ingredients to absorb UV light - the SPF 4 sunscreen was the worst performing UV blocker.

 

The results did not support the hypothesis that sunscreen would block UV light the best. Instead, rayon and sunglasses blocked UV light the best. In the first and second test the SPF 50 and sunglasses had the same results, but in the third test sunglasses performed slightly better than SPF 50. Nonetheless thick fabrics, sunglasses and SPF 50 are great sun-blocking materials.Background research explains that the thickness and weave of the fabric are important factors in UV exposure. The color and construction and fit matters as well. Also synthetic fabrics stop UV light better than natural fabrics. Rayon is thick and tightly woven, synthetic this helps explain why rayon stops UV light the best. For exposed skin, high SPF (sun protection factor) is better.

According to the Canadian Skin Cancer Foundation over 80,000 people get diagnosed with skin cancer in Canada each year. Besides limiting time in the sun, people can protect themselves from the sun’s harmful UV rays by wearing tightly woven synthetic fabric clothing. Sun protection clothes offer UPF50+ protection and are very effective, but are a bit more expensive than regular clothes. 

 

For exposed skin, you should apply sunscreen with a high SPF number and reapply according to the SPF rating. Buying a more expensive high SPF sunscreen is only a little more expensive than low SPF sunscreens, but you need to reapply far less often. Also, for your eyes, always wear sunglasses with UV coating. People with darker skin tones still need sunscreen, but are naturally protected by their skin’s pigment.

 

In the long run, you save money on sun protection clothing over continually applying sunscreen over a summer and you benefit by being protected from skin cancer.

 

The UV light exposure was calculated by the darkness of the beads and when I took the photos the lighting could have been different. Also the beads themselves could have been a problem, some beads may not have responded the same to the UV light. I tried to prevent this by taking out all the UV beads that did not respond at all. The sunscreens may not have been applied evenly. Another problem is the thickness of the fabrics, some fabrics were thicker than others for example, silk was thinner than rayon.

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2. Hot weather: How to stay safe in the sun. (n.d.). BBC. Retrieved from https://www.bbc.com/newsround/48609398

 

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4. CDC. (2024, June 27). Ultraviolet radiation. Retrieved March 20, 2025, from Radiation and Your Health website: https://www.cdc.gov/radiation-health/features/uv-radiation.html

 

5. Sunscreen. (2019, March 8). Retrieved March 20, 2025, from The Skin Cancer Foundation website: https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/

 

6.       (N.d.). Retrieved March 20, 2025, from Unc.edu website:   https://sph.unc.edu/wp-content/uploads/sites/112/2013/07/uv_beads1.pdf

7.    Sunscreen. (2019b, March 8). Retrieved March 20, 2025, from The Skin Cancer Foundation website: https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/

8.  (N.d.). Retrieved March 20, 2025, from Cosmoderma.org website: https://cosmoderma.org/history-of-sunscreen/#:~:text=1935%3A%20%20Eugen

9.  Barth, J. (1987). Johann Wilhelm Ritter (1776-1810) and the discovery of ultraviolet irradiation 185 years ago. Der Hautarzt; Zeitschrift für Dermatologie, Venerologie, und verwandte Gebiete, 38(5), 301–303.

 

10.  CDC. (2024, February 20). Facts about ultraviolet radiation. Retrieved March 20, 2025, from Radiation and Your Health website: https://www.cdc.gov/radiation-health/data-research/facts-stats/ultraviolet-radiation.html

 

11. Solar-powered chemistry: Study chemical reaction rates in ultraviolet beads. (2010, January 8). Retrieved March 20, 2025, from Science Buddies website: https://www.sciencebuddies.org/science-fair-projects/project-ideas/Chem_p088/chemistry/chemical-reaction-rates-in-ultraviolet-beads

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14. Sun protective clothing. (2018, July 23). Retrieved March 20, 2025, from The Skin Cancer Foundation website: https://www.skincancer.org/skin-cancer-prevention/sun-protection/sun-protective-clothing/

 

I would like to acknowledge my sister for helping me with the colour averager website and the citations.