Page 57 - Studio International - April 1970

The open

empire

Gene Youngblood

There have been some impressive statements
recently in information-oriented technological
art regarding the subject-object relationship,
but none so radically unprecedented as the
spherical mirror developed by the West
Coast branch of Experiments In Art and
Technology (EAT) for the Pepsi-Cola
Pavilion at Expo '70 in Osaka. While it was
manifested out of the synergetic technologies
of computer science and poly-vinyl-chloride
(PVC) plastics, it is triumphantly non-
technical as an experience. It's just a mirror.
A mirror which is nearly two-thirds of a sphere
made of 13,000 square feet of air-inflated
mirrorized mylar one-thousandth of an inch
thick. It is 90 feet in diameter and 55 feet
high. It weighs approximately 250 pounds.
At manometer air pressure of three-eighths of
an inch displacement it registers 25,000
pounds lift. My immediate reaction was that
I had never seen anything so astonishing, so
spectacular, so radiantly sensuous, so trans-
cendentally surrealistic as this giant mirror-
womb.
There have been other mirrorized mylar (or ultimate triumph of the project. If a hemi- Wide-angle view of EAT hemispherical mirror in
PVC) spherical tensile structures, notably the spherical structure were the only requirement, blimp hangar at Marine Corps Air Station in Santa
Ana, Calif. Specifications: 13,000 square feet of
Paeos and Echo satellites. But they weren't surface discrepancies of a quarter-inch here mirrorized mylar 1/1000th in. thick, air-inflated to
constructed as mirrors per se, and of course one and there wouldn't make much difference. 210-degree hemisphere 90 ft in diameter and 55 ft
high
could not enter them. The idea of a spherical But a mirror surface must be absolutely
2
mirror was first conceived by Robert Whit- smooth to avoid image distortion. Moreover, Three-dimensional holographic 'real image' photo-
man, a founding member of EAT in New lightwave dispersion is magnified in a con- graphed in reflections of EAT mirrorized mylar
hemisphere
York. Although Whitman has worked bril- cave surface such as the interior of the mirror: Photos: Peter Smokier
liantly with mirrorized mylar on several the smallest imperfections become giant
occasions, he had not suggested it for this incoherences. In a convex surface such as the
project. 'When we first began,' explained exterior of the mirror the image becomes
EAT's Western Regional director David smaller and more coherent. It was discovered
MacDermott, 'the problem was that we that in a concave space of 45-foot radius the
weren't simply building a structure. We didn't optimum surface deviation tolerable without from which light will disperse at 90-degree
ask ourselves initially, how do you build a apparent distortion was one minute of one angles.)
mirrorized mylar dome ? The question was, degree. (In structural design a 'minute' is a Since only a few millionths of an inch surface
how do you build a hemispherical mirror? unit of measurement amounting to 1/60th of a warp was all that could be tolerated the
We were building a surface.' degree. The minute on the mirror surface is obvious answer was a tensile structure in
This proved to be the major obstacle and the measurement of the warp in the surface which PSI stress is omnidirectionally equal.