To quote a post from Rain Noe (hipstomp from Core77):
I can’t lie, I find the stools and chairs ugly as sin, yet cannot stop staring at them in awe of the production method.
Making their American debut at Moss’ Poetic License exhibit in NYC, Oskar Zieta’s stools and chairs, originally designed in 2008, are fabricated by inflating welded steel. Think of those ultrasonically-welded vinyl inflated characters, except much more rigid and a tad more difficult to pull off.
Zieta developed his technique at the CAAD department at ETH in Zurich:
We can control the three-dimensional form by the two-dimensional shape of the sheet steel. The products that use this cut and welded steel can then be inflated anywhere, which makes this technology very flexible. All you need is the template and a welding robot. Before they are inflated 100 of my stools will fit on a pallet, although if they were all blown up they would fill up a container.
[More of his interview with Architonic]