Liquid Hourglass

Liquid Hourglass

Since it's almost time to turn our clocks back for Daylight Savings, it's fun to think about new and interesting ways to keep time. I'm sure you've heard of an hourglass, but did you know that you can make one out of liquids? We recently made this liquid hourglass using water and vegetable oil for a mesmerizing result. With just a few simple materials, you can create your own!

7 - 16
Est. Time:
<30 mins

How we did it:

Materials List

  1. clear water bottles (2) - they must be identical)
  2. drinking straws (2)
  3. drill
  4. scissors
  5. duct tape
  6. vegetable oil - (enough to fill a bottle)
  7. water - (enough to fill a bottle)
  8. markers - (optional)
  9. food coloring - (optional)
  10. funnel - (optional)
  11. hot glue - (super glue)
  1. Remove the two caps from the plastic bottles and use hot glue or super glue to attach the top of the caps. Make sure you get a good seal by pressing them towards each other.

    Tip: Let an adult handle the hot glue or super glue!

  2. Once the glue is dry, add a strip of duct tape around the conjoined caps to ensure a liquid-tight seal.

    Using your marker, mark two dots on one side of the cap. You will be using the dots as reference for drilling holes.

  3. Before you start this step, make sure to let an adult handle the drill.

    Find a drill bit that has the same circumference as the straw's. Using the drill, drill the two holes through the caps. Don't worry about using a drill bit that is a bit bigger than your straw's circumference!

  4. Cut out two 2" long straws. Fit one straw 1/3 down through one hole. Fit the second straw on the other side, 1/3 down through the second hole.

    If the straws don't have a snug fit, use hot glue or super glue to secure them.

  5. Remove any wrappings around your plastic bottles.

    Take one bottle and fill it up with vegetable oil using a funnel. Fill the bottle nearly to the top, stopping about 1 cm from the rim.

  6. Fill the second bottle with water. Make sure to stop at at the edge where the cap closes.  

    We added some blue and red food coloring to spice up our liquid hourglass! Add any colors you wish - just note that eventually the colors will mix, so ours turned purple-ish.

  7. When the glue on the straws is dry, screw one of the caps onto the bottle of oil.

  8. Quickly flip over the bottle of oil and screw the other cap onto the bottle of water. Flip your hourglass over again so that the oil is on the bottom, and the water is on top. Watch as the exchange of liquids mimics an hourglass!

    Tip: Make sure you don't squeeze the bottles as you're turning them. It's easier than it seems!

    What's going on:

    In this experiment, you saw that the oil floats on top of the water. This is because the water is more dense than the oil. Density is a measure of how tightly packed a material is. When oil and water come together, the water will sink to the bottom, while the less dense oil floats to the top. Because the liquid has to pass through the holes in the lid, this happens drop-by-drop, creating your oil-and-water hourglass!