A curtain wall is the architectural term for a special cladding
treatment. Like all cladding, it forms a skin on a structure which does not
aid in supporting it; a curtain wall merely serves to keep the elements at bay,
or to nominally separate spaces within a structure. Historically, the fortification wall
surrounding a castle is also called a curtain wall (see the URL below).
Curtain walls have most famously been applied in modernist skyscrapers, often
giving them an almost seamless stone or glass exterior. It is (or was, before
it became a cliché) architectural legerdemain to have a vast building
almost etherially disappear into the sky as it reflected blue and clouds in
a mirrored glass skin. To appreciate it, it's important to think yourself
back into the mindset when everyone expected buildings to be ponderous, heavy
objects, even if, like a skyscraper, they had a certain sky-piercing energy.
If all the skyscrapers you'd ever seen were stone or brick piles like Sullivan's 1892 Wainwright Building in Saint Louis, or Van Alen's 1930 Chrysler
Building (both magnificant structures, by the way--see the URLs below),
you can readily see how Gordon Bunshaft's 1952 Lever House,
or Mies and Johnson's nearby 1958
Seagram Building, with their almost total glass curtain walls
on steel frames, provoked strong reactions.
Credit for the first glass curtain wall probably belongs to Willis Polk's astonishing
1918 Hallidie Building in San
Francisco. Although the exterior of the structure has not totally disappeared
into glass, the transparent glass walls of the central block of the building
are in fact held out some feet from the steel structure by brackets, giving
the guts of the building a sense of floating within. Frank Lloyd Wright's
1949 Johnson Wax Company Research and Development Tower in
Racine, Wisconsin was also pioneering in its use of glass curtain walls (made
of glass tubing!) between floors cantilevered out from a central building core.
Not all modern skyscrapers have steel frames with a curtain wall. Yamasaki's
1972-73 World Trade Center Twin Towers supported themselves
with a tight steel mesh on the exterior of the building which failed structurally
in the heat from the gas fires after the planes struck them.
URLs.
http://www.castles-of-britain.com/castlesy.htm (Page dedicated to castle curtain walls.)
http://www.som.com/resources/projects/2/1/5/printPreview.html (Lever
House, from Skidmore, Owings and Merrill site.)
http://www.greatbuildings.com/buildings/Lever_House.html (Lever House,
photos.)
http://www.galinsky.com/buildings/seagram/ (Seagram Building.)
http://www.greatbuildings.com/buildings/Johnson_Wax_Building.html (Johnson
Wax Research Tower.)
http://www.bluffton.edu/~sullivanm/wainwright/wainwright.html (Wainwright
Building--the pictures do not do justice to its color.)
http://www.greatbuildings.com/buildings/Wainwright_Building.html (More on the
Wainwright Building.)
http://www.greatbuildings.com/buildings/Chrysler_Building.html (Chrysler
Building.)
http://www.greatbuildings.com/buildings/Hallidie_Building.html (Hallidie
Building.)
http://www.mistersf.com/props/index.html?propshallidie.htm (Hallidie
Building pictures.)
http://www.greatbuildings.com/buildings/World_Trade_Center.html (World
Trade Center Twin Towers.)
Note. Friends, please bear with me as I issue a few shorter writeups defining a variety
of architectural terms I'll need to draw upon for some larger writeups I have in the pipeline. I'll write up a collected list
somewhere on the model of Dawggy's useful collection of nodes on poorly-known female artists.
(And in any event, it's always worth adding factual content to the gel.)