Dilatancy of Deformation
close packing - deformation
What it shows:
When sand in a balloon, just as atoms in a lattice, are close packed, they occupy the least possible volume.
Any deformation, even compression, deforms this close-packed arrangement causing an increase in volume.
How it works:
The balloon is filled with sand, and black ink added allowed to percolate down and fill the air gaps. A
capillary tube sticking out of the balloon indicates the ink level. When the balloon is squeezed the sand,
which had settled down to a closely packed arrangement, is dislocated. Larger gaps open between the
grains which fill with ink, and the ink level in the capillary drops.
Setting it up:
Take any normal round balloon and loosen it by blowing it up a few times. Load it as full of sand as you can
using a funnel, then add the ink similarly. Give it time to drain; you'll know when its saturated when the ink
level doesn't drop. If your ink is too soupy, it can be watered down. The capillary tube should be about 20cm
long with a 1 - 2mm bore. Stick the tube about half way into the balloon, and let it sit to reach equilibrium.
Camera setup with macro lens to show the ink level against a white backdrop.
Comments:
What a mess! Balloons burst, sand and ink everywhere. Aesthetically gruesome, but it does work.
Very counter-intuitive. Rating**