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How to Make Clay Float in Water

If you drop a quarter into a wishing well, it sinks down through the water to the bottom of the well with all the other wishers' coins. If you take a second quarter, build a wall around its edge with a piece of masking tape and place it in the water with the taped walls facing up, it will submerge slightly and then float. An object floats when its density is less than the water it is immersed in and its buoyancy is the equivalent of its displacement of water. Clay can also be manipulated into forms that will float.

Things You'll Need

Non-hardening clay
Bucket
Water
Paper towels
Pennies
Ice pop sticks
Waterproof marker
Ruler
Light source
Masking tape

Instructions

- 1
  Mark the inside of the bucket 3 inches from the top with a waterproof marker. Fill the bucket to that mark with water. Make a ball out of a small handful of clay and place it in the water. Mark the water level after the clay has fallen to the bottom of the bucket and compare it to the original mark. The change in the water level is the result of the clay's displacement of it.
- 2
  Remove the clay from the bucket and pat it dry with paper towels. Press it flat on a clean surface and then mold it into the shape of a boat with a flat bottom and sides. Make sure your boat is air-tight by inspecting it in front of a light and looking for any holes.
- 3
  Put the boat into the bucket and note how much it sinks before floating. Place a mark at the new level of the water. This mark should be located between the original level and the one made when you submerged the clay ball. The clay boat stops sinking when the amount of water it displaces is equal to its buoyancy.
- 4
  Test your boat by loading it with pennies that are spread evenly on its deck. Continue doing so until the boat sinks, then compare the water level at that point to the other marked levels.
  Make a note of how many pennies the boat was able to hold before it sank.
- 5
  Make a second boat with another ball of clay. Alter the design of this boat by making the bottom rounded and the walls higher. Mark the level of water displacement after placing this new design in the bucket, and repeat the penny test. Compare the cargo capacity of this design to that of the original boat.

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