Microwave Grape Plasma
Its the damnedest thing you've ever seen. Please realize that although we
haven't actually damaged any of the ovens we've done this with, the potential
exists to damage or destroy the microwave that this is done in, and the
possibility also exists that it could harm a human being if the proper
precautions are not made. Please see to it that you are willing to pay $200
for a new microwave before you try this, and that you have a fire extinguisher
nearby. If you are under age 18, please seek the supervision of a parent or
guardian. I accept no responsibility should this experiment cause damage or
injury. How to make a glowing ball of plasma in your microwave with a grape:
Find your microwave hotspots Take a damp paper towel and
place it on top of 5-10 other paper towels in the bottom of your microwave. On
top of it, place a sheet of themally sensitive fax paper, the kind that old
crappy fax machines use. Credit card recipts also work, but they'd be harder to
tile the bottom of your microwave with. The extra towels at the bottom provide
some insulation. Turn the microwave on for a while. The first areas on the
paper to turn dark are the hot spots
Grape preparation Cut a grape in half equatorially (assume
that the stem goes through the pole). Then place the new cut surface against a
paper towel or other paper product to dry it. Don't squeeze it to death, but
try to try it as much as possible. Lay the grape half with the wet side up, and
slice it in half top to bottom, leaving a small (~3-7 mm) bridge of skin between
the halves. Dry the new surfaces.
Plasmification Place the grape with the cut ends up like two
adjacent bowls on a plate or saucer of some sort and place the grape in your
microwave's hotspot. Turn on the microwave for 15 seconds.
Troubleshooting Normally to keep the grape in the hotspot you
should remove the turntable, but if you aren't getting a show, try putting the
turntable back in and letting the grape explore the microwave by being turned
around all over it. Really make sure that the ends are dry, as if they're wet
they tend to short-circuit across the ends and you don't get electrical
What's going on? Well, I only have an idea for some parts. The first part is
speculation -- the sparks are resulting from an electrical discharge between the
sides of the grape, as is evident by watching and as supported by the 120Hz buzz
that coincides with the grape flaming. It could be that the particular size of
the grape relative to the wavelengths of the microwaves in the oven causes the
discharge, but I don't know if I believe this yet. What is the mechanism for
The discharges vaporize the sugars in the grape and then cause them to combust.
The combustion products, if they get hot enough due to the continued electrical
arcing, form a plasma (gas where the nuclei and electrons have been ripped apart
from one another). This plasma is electricially conductive, and so absorbs
microwaves keeping itself warm, and causing the cloud to glow. Since the cloud
is hot, it rises to the top of the oven. However, the cloud seems to stay
remarkably coherent. Why doesn't the could dissipate over timescales of
Cut your grape in half, then cut the half into halves (quarter-grapes) leaving a
small bridge between the halves. Dry the cut surfaces.
Place the cut crape with the cut surfaces up onto a platter.
Put them in the microwave's hot spot.
Within 3-4 seconds of turning on the microwave electrical arcing between the two
grape quarters emits light, a buzzing noise, and periodic flames as the sugars
in the grape burn.
If you've been lucky and good, you may get treated to a show of a ball of
glowing plasma rising through your microwave oven.