From Stevespanglerscience.Com

UV Beads

From Stevespanglerscience.com:

UV Beads have a chemical substance embedded into the plastic that will change color when exposed to UV radiation (sun light). 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.

Materials

Color changing UV beads Zipper-lock bags String Different types of sunscreens Newspaper to cover the table and/or paper plates Fluorescent light source Sunglasses

Some experiments to try…

Sun Screen Test

With all of the SPF (Sun Protection Factor) numbers available, we want to know what SPF lotion really works best at keeping out the sun's harmful UV rays? Start by collecting various strengths of sunscreen (SPF 4, 15 and 50, for example). Since the UV Color-Changing Beads are very sensitive to changes in UV energy, you can use the beads to determine the blocking potential of the sunscreen. Place the beads in a zipper-lock bag and apply a layer of sunscreen to the outside of the bag. Use a permanent marker to write the SPF number of the sunscreen you're testing on the outside of the bag. Be sure to set-up one bag without any sunscreen coating for comparison purposes. Expose the beads to direct sunlight for 5 minutes and look for any changes in color.

The beads will always change color regardless of how good the sunscreen blocks UV - the beads are very sensitive! The key is to rate the color of the beads on a scale of 1-5, with 5 showing the most color or "burning" and 1 showing the least color. The bag without any sunscreen is an automatic "5". You can also test the difference between new and old sun screen. Sunscreen manufacturers suggest that you throw away old sun screen because it does not block out harmful UV light. Do your tests support this claim?

Light Test Place a handful of UV beads near a fluorescent light. Do any of the beads change color? Can you get a sun burn or a tan by sitting next to a fluorescent light?

Black Light

"Black light" (long wave ultraviolet light) can also be used to change the color of the beads. You can purchase a black light at many specialty stores or hardware stores that have a large section of light bulbs. Steve Spangler Science also sells them. Sometimes those high intensity lights (mercury vapor) found in a gymnasium emit just enough UV light to make the beads barely change color.

Sunglasses

Test the ability of your sunglasses to block out ultraviolet light by covering a few beads with the lens of your sunglasses. If the beads do not change color, your sunglasses block out harmful ultraviolet light from your eyes. If not, you paid too much for that UV coating!

Potential problems with this experiment:

 Give kids a bottle of sunscreen and ask them to spread it on a plastic bag and chances are there will be sunscreen all over the table and windowsills when they are done! You could use newspaper to cover the tables and/or bring paper plates that the kids can put their bags on to avoid a mess. This should save time on clean up as well.  Kids may decide it’d be fun to take the beads out of the bags and throw them around! You could tell kids ahead of time that if they keep the beads in the bag for the experiment, then they can take them out and make a bracelet using the string afterwards. Warn students that if they throw beads, they won’t be able to keep them in the end. Letting them keep the beads on a bracelet also reduces the chances that they will scatter the beads all over the floor between the time you leave and the time they go home.  The kids may all want to use the “best” (highest SPF) sunscreen for their beads, which may lead to sharing problems and weaken the overall variance you will see in UV protection from the sunscreens. Avoid this problem by writing an SPF on each of the bags with a sharpie, and distributing the bags randomly to the kids. Then tell the kids to use the sunscreen with the SPF that matches the number on their bag.  Kids that have the control, no sunscreen bags may lose interest when watching their peers put sunscreen on their bags. Let all of the kids put sunscreen of some sort on their bags and bring an extra control bag.  Have a backup activity in case you don’t see a lot of change in the beads or be prepared to go outside to see the changes happen.