The welding robot, which seals together the edges of two cut-metal pieces so they can be blasted full of air, eliminating the need for an expensive mold. It sounds like a simple idea, but it took Zieta a lot of problem-solving to refine. His first experiments in 2003 were with water pressure rather then air; either way, there was the issue of seaming. “We have many different metals we can use in the welding process, and I tested all of them,” he says. “We had to make the connection strong enough, and without any small holes.” When he began to move on to larger sculptural pieces with dozens of separate FiDU elements, he then had to figure out the connections between those.