Tornado in a bottle

Here's what we used:

2 - 2 liter bottles
duct tape and gorilla tape
scissors
glitter (optional)
dye (optional)
water

What we did:
Fill one bottle about 3/4 full with water. If desired, add glitter and dye now. I used yellow dye and yellow glitter, I suggest using two different colors so there's more of a contrast. Turn empty bottle upside down and tape the two openings together very securely. We first used duct tape and then went over it with gorilla tape. Once secure, turn the bottles over and rotate around a few times. The tornado should form at this point. If not, practice with the rotating and you should get it.

The finished product:

I may try this again with some smaller water bottles. Not sure it will work, will let you know. But these bottles are really heavy and for a 4 year old to flip over and rotate. We'll see if the smaller ones work. I had to show the boys a video of a tornado on youtube first since they didn't know what a tornado was. Then Nate says "Wow, can we see one in person sometime??" Ugh, I hope not!