"What the directors described was an arm almost beyond what Tony Stark could do now, the highest tech possible, so whoever had replaced Winter Soldier’s arm was beyond what even our main technological hero of the Marvel Universe could accomplish," Meinerding says. "That allowed us to go with the horizontal cut lines across the arm, something fairly traditional in the Marvel Universe, so it was kind of cool to be able to do it on-screen."
Shane Mahan, Physical Suit Effects Supervisor at Legacy Effects, describes the process of creating the Winter Soldier’s arm from a life-cast of actor Sebastian Stan: “First, we do an exact mold of the actor’s arm for the size and the dimension, and then we do a casting out of that. But we also took him to get a 3-D scan of his arm, so we had digital information as well as a hard, real-world casting to work from. We took the designs from Ryan Meinerding’s design team, and then one of our digital artists here — Won-il Song — created a digital sculpture.”
"I designed this to be a seamless forearm piece," Mahan continues. "And after the digital sculpture has been done, and the part has been grown and cleaned up, it matches up to a bicep piece. One of our artists, Chris Swift, is pictured testing it."
Legacy created two versions of the Winter Soldier’s arm. “We made one from foam rubber with tracking markers on it for extreme action,” Mahan says. “And then there were these arms made of urethane that were metalized and had less action mobility, but for certain shots looked reflective and really great.”