How to Construct a Water Clock

Constructing a water clock involves setting up a steady flow of water to measure time. The National Institute of Standards and Technology's website states that one of the first known water clocks came from an Egyptian tomb dating from approximately 1500 B.C. Nearly 1200 years later, the Greeks developed water clocks called clepsydras, "water thieves," out of stone receptacles. Water clocks are among the earliest time keeping devices. They allowed ancient people to keep track of time indoors. Explore this ancient breakthrough by making a water clock from common household objects, or build an attractive conversation piece for your home or garden.

Things You'll Need

• Large metal can or basin
• Clear glass mayonnaise jar
• Nails, different sizes
• Protective goggles
• Hammer
• 3 self-adhesive labels
• Scissors
• Waterproof marking pen
• Clock or watch with second hand

Instructions

1. Use the hammer and a nail to make a hole in the bottom of the can or basin. Harvard University's Hands On Astronomy website recommends using a coffee can and a jar strong enough to hold it when it's full of water.

2. Remove the backing from an adhesive label and press the label lengthwise to the side of the jar. Apply the other two labels so that there is one long strip from the bottom of the jar to the top. Cut off any extra label paper at the top of the jar.

3. Pour water in the can. In a classroom, set the can on the jar to test it. Fill the can or basin with water. Watch to see that the water flows evenly. If it stops and starts or dribbles, empty the water and use a thicker nail to make the hole larger.

4. Empty the jar if you used it for the flow test. Fill the can with water and center it on the jar. Check the time, including the position of the second hand. Watch the clock as the water flows into the jar.

5. 

   A stand with basin and a pot works for a water clock.

   Use the waterproof marker to draw a line at the water level when 5 minutes have passed, then 10 minutes, 20 minutes, 30 minutes--and at 10-minute intervals for as long as the water runs. Write the number of minutes next to the water level line so that anyone reading the clock can tell the time.

6. Reset the clock by emptying the jar and refilling the can.

Tips & Warnings

• Use bigger containers to measure longer spans of time.

• Use an enamel basin and pitcher set with a bucket or pot beneath it to create a decorative water clock. Make a hole in the basin and put it on the top of a plant stand with a pot or bucket below it. Use the pitcher to refill the water clock. Mark the time lines at the water level for the hours inside the pot or bucket with a nail point. Dry the pot or bucket, then paint the water level lines and numbers of the minutes and hours.

• Put on the safety goggles to make a hole in any object that could fragment, such as pottery or enamel. Direct anyone nearby to stand back. Be careful with enamel basins, because the enamel can chip off and the flakes are sharp.

References

• The National Institute of Standards and Technology (NIST): Early Clocks
• Harvard: Hands On Astronomy: Water Clock Activity

Resources

• Read this Article in Spanish