Essentially cornstarch is a fluid whose viscosity is rate dependent. You can hit it hard with a spoon and it will strike it and bounce off, but can be spooned slowly and drip from a spoon. A real anti splash fluid.
“Continue reading” about this zany zombie fluid. 9 photos.
Here is how made my own cornstarch fun. Also spelt as separate words – corn starch and corn flour here in Australia. Also known as “oobleck” is derived from the Dr. Seuss book Bartholomew and the Oobleck.
On a flat plate under vibration the vibration is probably more marked at discontinuities and edges (like a wave breaks at the seashore). This leads to bizarre effects with cornstarch which gets forced up into stalagmites, loops and bizarre writhing spooky shapes like pools of writhing undead…
Anyway it is very easy to do. Get the wife/girlfriend/significant other to make a reasonably thick cornflour/cornstarch mixture. This is a common cooking ingredient and is used in about 1 part of water to 1.5–2 parts of cornstarch . Get a small loudspeaker (I used 4 inch, 4 ohm, 3.5 W) and feed it with 50 Hz / 60 Hz. I guess the speaker can still be in its enclosure. Don’t get cornstarch over your home theatre speakers though as this will upset the wife/girlfriend/significant other.
Use a 6 VAC transformer or winding with a dropping resistor of 8 – 10 ohm 5 watt, or use a variac. Even use the other speaker of a stereo pair as a dropping resistor. I needed about 2.0 VAC i.e. 0.5 W.
Place some plastic cling film (Gladwrap in Australia) loosely over the speaker so that a spoonful or two of the cornstarch mix will sit closely applied to the speaker cone.
I did try a frequency generator and different frequencies but 50 Hz seems fine, particularly as it dries a little and the viscosity rises.
Photos above show varying effects as the power is increased.
I tried this with a sub-woofer and the results were a bit disappointing initially.
The 12 inch sub-woofer driven with 40 W at 50 Hz (12 VAC). There is only limited extension of the cornstarch. Removing the plastic had little effect until I got out the frequency generator and a 100 W audio amp and picked out the resonant frequency of about 22 Hz where cone excursion was greatest and up to one inch.
Spooky stuff
The 12 inch sub woofer driven at 25 Hz where the cornstarch lumps get thrown around. Zombies appear.
You can get some unusual shots with the funny properties of cornstarch. Here I was pouring it out with a spoon. The pour is falling but nowhere near as fast as it should.
Related pages
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External links
Corn starch – Wikipedia
Non-Newtonian fluids – Wikipedia
Photo Date: Oct 8, 2006