The supine man in the shower cap with two straws stuck up his nose was not being treated for art-fair fatigue: he was about to be immortalized in plaster by John Ahearn and Rigoberto Torres. It's an art form that Ahearn, who has collaborated with Torres from the beginning, has been practicing since 1979, when he first gained attention for the "South Bronx Hall of Fame," a series of painted live plaster casts of people from the local neighborhood, which was shown at the Bronx gallery Fashion Moda.

Those original plaster casts, not shown together since that time, lined the booth for Ahearn/Torres' commissioned Frieze Project, where visitors could sign up for a live plaster cast of themselves for $3,000 a pop. By phone from the fair on Saturday, Ahearn told A.i.A. that he and Torres still get their inspiration from "these pieces we haven't seen in more than 25 years, the people behind the people, giving us ideas as to how to make these pieces now."

On the first day of the fair, collector Ellen Stern submitted to the two-hour treatment, which consisted of several phases, the longest being a "psychological assessment" in which Ahearn and Torres "see if [the sitter is] prepared for the rigorous task ahead" by asking such key questions as "Do you like swimming?"

"I walked by and thought this would be fun," said Stern. "I loved their work in the South Bronx. I think it's quite a wonderful concept, capturing the real looks of people." She and her husband, Jerome, had intended to do it together, but he got nervous about the straws.

The casting itself is the shortest part of the process: first a thin coat of dental plaster is applied. The next layer is made up of fast-drying plaster bandages packed on mummy-style. Once it sets, the mold is peeled off, and the piece mold is cast. The actual casting takes 15–20 minutes; Ahearn and Torres later carve and hand-paint the live cast, using a digital photograph they have taken of the subject as reference for coloring.

"Technically, we're back in the stone age," Ahearn said of the method. "We are so retro in terms of material that we worry about some of the products we use being manufactured in the future. The most challenging aspect is our relationship with the people we cast. The rest of the process is insignificant and really easy. Casting is a piece of cake. Anybody can do it. It's embarrassing."

Since 1979, Ahearn and Torres have completed major public projects in Taiwan, Puerto Rico and Brazil. They created three pieces at a train station just outside of Taipei; a wall embedded with busts of children from the local elementary school; a street scene of scooters; and one of people crossing a wooden bridge. Their Puerto Rican project, at a sports complex, is  a bas relief of images related to boxing, swimming and basket ball. Their project in Inhotim, Brazil, is a huge double mural; all outdoor pieces are cast in fiberglass.

The front window at Fashion Moda, where Ahearn originally cast the gallery's founder, Stefan Eins, may be a far cry from a booth at the first edition of Frieze New York. But judging from the enthusiastic reception, the original formula still works. By fair's end on Monday, 12 live casts had been made. For the artistic duo and their subjects, it was a one-time opportunity. "We've never done commissioned casts before, and we have no plans of doing them in the future," Ahearn said. The artists have their work cut out for them: completing the Frieze casts will take about a month.