Materials:
can of lighter fluid
CO2 fire extinguisher
lighter or matches
damp driveway
cool dark evening
Hose down your driveway (or sidewalk, for the small version)
Use the can of lighter fluid to squirt lines of flammable liquid on the
wet surface.
Touch it off with a match.
The above would just be simple arson, were it not for the fascinating
patterns which develop. The result is not a flaming pattern, instead it
is a small blue "will-o-wisp" flame which rushes to and fro along the
lines of lighter fluid.
If you create a fairly thick pool of liquid, it will burn continuously and
will act as a central generator for the small blue flames. A thick pool
connected to a thin line of liquid will generate a row of moving blue
flames.
I presume that this is caused by buildup of flammable vapor over a shallow
pool of liquid which is too cool itself to burn. The flame front rushes
over the liquid and consumes the vapor, leaving no flame in its wake, and
the vapor builds up again for the next flame front.
If you draw a circle and touch a flame to one point, two little flames
will rush off in opposite directions, only to annihilate each other when
they meet at the opposite side. Knowing the "jellyfish neurons" effect,
where permanent standing waves can be induced on moon jelly rims, I
performed a similar trick. Make a lighter-fluid circle, place a
(nonflammable!) object to block the path, then touch a match to the
circle and remove the object. The object extinguishes the flame front in
one dirction, and the flame front going the other way will rotate in the
circle many times (maybe even continuously until the fuel is exhausted.)
A circle having some straight paths connected to it will launch periodic
flames down the straight paths as the circulating pulse divides at the
junctions.
A narrow track with a burning pool at either end will create a battle
between the flame fronts, and the location of the annihilation point will
drift back and forth. Momentarily interposing an object in the path can
reset the "null point".
Burning pools, parallel tracks, circles, and branching tracks can be
created which give complicated flame patterns. The lighter fluid tends to
evaporate quickly, so work fast when creating new patterns.
I expect that all these can be visualized with a Cellular Automata
simulator. In the real world, the flame fronts duplicate the wavefronts
of heart beat on cardiac muscle. Burning pools act as pacemakers, and the
medium has a natural recovery time. The tail-chasing circle-oscillator
flames are an accurate simulation of heartbeat waves occurring during
ventricular fibrillation.
Do I need to point out the many dangers in doing this? Make sure no
flammable materials (leaves, dry lawn, etc.) are near your driveway.
Obviously don't try this indoors! Use only lighter fluid (naphalene, I
think?) Never spray more fluid on a pattern that's already burning. Take
care to avoid the missing leg-hair effect (and the possible human torch
effect!)
- Bill "still gots all my leg hair" Beaty
P.S. Dry ice in a 2L plastic soda bottle makes a passable "firecracker",
and dry ice is usually easier to obtain than LN2. Be aware that dry ice
bombs can take up to a couple of hours to pop! Watch out, sometimes the
neck assembly of PET bottles fractures, and launches a dangerous heavy
fragment. Idea: wrap nichrome wire around a pressurized soda bottle in
order to electrically trigger the blast. Build seventeen of these wired
to a keyboard and treat the neighborhood to Blue Danube Waltz, "Exploding
Version." The Exploding Version of the William Tell Overture would take a
couple of hundred... ;)
......................uuuu / oo \ uuuu........,.............................
William Beaty voice:206-781-3320 bbs:206-789-0775 cserv:71241,3623
EE/Programmer/Science exhibit designer http://www.eskimo.com/~billb/
Seattle, WA 98117 billb@eskimo.com SCIENCE HOBBYIST web page