After seeing Brett Carrol's demo at AAAS of stressed gelatine between
crossed polarizers I just had to try it. My version is a rectangular
plexiglass cell 6" x 6" x 2", with one narrow side open, full of Knox
gelatine at double strength, with a large iron bolt suspended near the
bottom on fishline. Sure enough, when the cell is placed between
polarizers in front of a white surface, pressing on the exposed jello
causes a colorful stress-field to blossom in three dimensions around my
fingertip. A large magnet does the same when held near the bolt. Or one
can simply pull on the embedded fishline.
But even better: when I knocked the device against the table, a
complicated array of dark and light bands appeared momentarily. A tank of
hardened jello between crossed polarizers appears to form a sort of
"Chladni plate", but with three dimensional patterns instead of two! Now
I have to rig up some sort of variable frequency vibrator, so I can create
all sorts of visible 3D Bessell functions within the cubical volume. Looks
like Star Trek effects, but uses decades-old technology.
Also, I tried sending an ultrasound beam through the material. I had
visions that the beam in the jello might become visible, unlocking all
sorts of demo possibilities. No such luck. The beam apparantly doesn't
stress the jello enough to make visible effects. I did manage to melt a
spot in the plexiglas wall, though, which did cause stress patterns to
appear (in the plexi.)
Aside: everyone should take apart an ultrasonic humidifier and add
extensions to the transducer wires and insulate with silicone caulk. It
*must* only be operated under water. The output is a tight beam of many
watts, which can melt plastic tank walls, write your initials on thermal
liquid crystal postcards, trap bubbles in standing waves when vertical,
etc. Should burn flesh too, if you aren't careful.
Has anyone here used gelatine in long term exhibits? What works good as a
preservative? I've made jello-tanks before (Tyndall effect) but find that
they also serve as 3-D petri dishes, with spherical mold and bacteria
colonies propagating through the volume like expanding supernova shells.
Cool demo in itself, but I was wanting physics, not bio!