How can i help my son create a one minute timer using household items?

Question:

How can i help my son create a one minute timer using household items?

and...we have to create it now. its for school tomorrow. we have tried sand,sugar and cat liter, in bottles, but they all stop half way thru. even with big holes, little holes, it doesnt work. ahhhhh what can we use?

Additional Details

2 days ago
shootingstars...u cant be serious can u? come one now. you missed the question all together. reread it, then edit your answer.

2 days ago
joseph, thanks for the hourglass idea, we are about to try it now. we tried a water based one too. lack of oxygen made it stop too.

Best Answer - Chosen by Asker: 2 days ago
shootingstars...u cant be serious can u? come one now. you missed the question all together. reread it, then edit your answer.2 days ago
joseph, thanks for the hourglass idea, we are about to try it now. we tried a water based one too. lack of oxygen made it stop too. The key is to have an hourglass shape where the sand goes from one side to the other. Try making a cone with paper and tape.
Also, you might consider using a fluid-based timer. They don't jam like sand. one minute equals 60 seconds take a hard object and a stick and count one, one thousand two one thousand..........Simplistic but true........ I've seen this done with Corona beer bottles, but it was an hour of sand. Try it with the 2 small coke soda bottles (the glass ones). If you can't, maybe a hot sauce bottle or some form of a narrow bottle/container.
Forgot to include 2 caps (with holes), super glue, about 4 chop sticks (for support), and 2 plastic drink coasters for the base.