From: Ellen Koivisto & Gene Thompson (offstage@earthlink.net)
Date: Sun Feb 08 2004 - 18:36:23 PST
Date: Sun, 8 Feb 2004 18:36:23 -0800 Subject: pinhole CO2 question From: Ellen Koivisto & Gene Thompson <offstage@earthlink.net> Message-Id: <C00C992E-5AA8-11D8-9FB1-000A959C38A8@earthlink.net>
I do theatre on the side, and a science question has come up for an
effect we want in an upcoming production. I thought I'd try the
pinhole brain bank to see if anyone can help.
We want fog falling from the grid and an oil projector (think hippies)
projecting up into the fog. This is supposed to look like what someone
on too much acid would see if they saw a ghost. The usual fog machines
use this oil-based stuff that spreads out generally and is bad for the
lungs. CO2 fog stays together, disperses without mucking up the air
for a half hour or more, and sinks. We would place the oil projector
under the CO2-fall and shoot the light up into the fog.
The height from the grid to the stage is about 10' (theatre hasn't
discovered the metric system yet). The effect has to come about 10 or
so minutes into the show. There can't be fog before that time, and it
needs to stop after about 1 minute. The problems we've identified so
far are numerous. It's hot in the grid. The fog has to stop. The fog
has to be directed. The fog has to be adequate. The fog has to be
there on demand. And I need to be able to get CO2 four days in a row
without having a car.
OK, we figured that e could rig up something in the grid that would
hold the dry ice in a cherry basket, for instance, and lower that into
water (also up in the grid) via a rope and pulley system. A basin with
a lip slightly lower could direct the fog-fall. We could play around
with dry ice for awhile to see how much is needed to make an adequate
fall.
I'm more worried about if we need to have space in the basin to build
up some fog before it pours down and if we'd be able to make enough fog
for the projection effect to work. Also, anyone know where I could get
dry ice in SF, close to the Embarcardo? The show is going to be
performing at The Eureka, which is at Jackson and Battery. It's right
next to a Safeway. Do Safeways ever have dry ice?
Thanks,
Ellen Koivisto
SOTA, SF
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