A fun experiment combining simple electronics and common food stuffs. You'll need 4 cups of sugar, 2 cups of water, wire, electrical tape, assorted LEDs, paper cups, wax paper, a stove and a medium sized pot!
Step 1: Preparing the Sugar Syrup
Boil the 2 cups of water in the medium sized pot, adding the sugar 1 cup at a time and waiting for it to dissolve. It's important to keep stirring the pot and not to let the sugar cook too much or it will burn.
Step 2: Wrapping the LEDs
Take the LEDs, wire and electrical tape and wrap the wire around the leads, securing them with the tape. Wet the heads of the LEDs slightly and roll them in sugar to coat them and provide a base for the crystals to grow.
Step 3: Pouring the Syrup
After turning the sugar syrup off wait 5-10 minutes for it to cool, then pour it into either glass jars or paper cups. My first attempt was with glass jars but I found the crystallization took too long so I transfered the mixture to individual paper cups and that made it much easier. Wrap the ends of the wire around a pencil and lower it into the cups, adjusting the wire wraps to the height of the sugar line so that the head of the LED is totally immersed in the sugar.
Step 4: Unwrapping the Crystals
Set aside in a cool place away from direct light and wait 1-4 weeks, depending on how large you want the crystals to be. Peel off the paper cup from the sugar crystal and carefully break off the unconnected crystals from the main crystal formation around the head. Running it under warm water helps.
Step 5: Dry and Test
Set on a sheet of wax paper and allow to dry for a day or so. After completely dry, test with a 3V coin cell battery. You'll notice that the sugar helps diffuse and extend the luminosity of the LED to a much larger area.
Step 6: Play!
I'd advise you not to eat this experiment- LEDs are small enough to be accidentally swallowed so use caution if you do this experiment with kids. Have fun!