By ERIK PIEPENBURG

Published: September 10, 2012

Melissa Erdman has a killer recipe for vomit.

“Mixed-fruit oatmeal,” she said.

Ms. Erdman knows from bodily fluids. As a freelance props master (or “prop tart,” as she calls herself), her job is to buy furniture, make accessories, whip up batches of blood or do whatever else it takes to make sets look and feel as authentic as possible. Ms. Erdman was one of about 50 props people who gathered on Friday night at the Public Theater for an informal meeting that gave attendees a chance to network, watch demonstrations and exchange insider tips on the latest techniques in an area of theatrical design that often goes unnoticed and unheralded.

“It’s kind of the stepchild of theater,” said Faye Armon, a properties coordinator who works often at Lincoln Center Theater.

Theatergoers probably understand what costume, set and lighting designers do. Their work can be eye-catching, and their names appear on a program’s main credit page. They get their own Tony Award category. But a props master?

“Picture moving into a new apartment, and everything is bare,” explained Jay Duckworth, the Public’s properties master and the organizer of the gathering, now in its fourth year. What a prop person does is “make that apartment represent you or your girlfriend or your grandmother,” he said, “everything from the lights to curtains to pillows, to ashes in an ashtray.”

Degrees in props mastery are available, but many props people learn through apprenticeships with veteran props masters. The challenges of the job are mainly questions of how. How do you get a pregnant character’s water to break on cue? (Pneumatics.) How do you get an actor to bleed on his shirt but not his overcoat? (Strategically placed artificial-blood pellets.) How do you prepare an onstage buffet for 50 people eight shows a week? (Plastic food and Costco.) And how do you make weather realistic?

“When somebody comes in from a snowstorm onstage, it’s usually plastic, and it lives with them the whole time they’re there,” Mr. Duckworth said. “But snow in a can melts away.”

Several attendees said props masters were first and foremost jacks-of-all-trades. Mr. Duckworth described the ideal one as “extremely intelligent, socially somewhat awkward, an engineer, historian and autodidact.” A props person might be called on to know (or learn) a wide range of skills: sewing, carpentry, fabrication, mold making, antiquing, food styling, welding, upholstering, painting.

The work of a great props master is integrated subtly, almost imperceptibly, into a show. A piece of duct tape on a chair can quietly speak volumes about a character.

“You take the same chair and put a doily at the back of the head, and it becomes a different chair,” Mr. Duckworth said.

After the conclave opened with a spread of beer and cheese — at least it looked like beer and cheese — the participants sat down in one of the Public’s theaters for a demonstration of stage weaponry. It was led by the Specialists, a New York company that employs about 35 people with a range of expertise, from high-tech electronic design to antiquated fields like blacksmithing and sword making.

The weapons on display — guns, knives and swords — looked like a madman’s arms stash. Holding a realistic-looking handgun aloft, Rick Washburn, founder and president of the Specialists, said weapons that didn’t need to work onstage (what the company calls “holster stuffers”) were usually made of plastic or rubber. Guns that need to fire are often the real thing extensively modified to shoot only blanks.

Nigel Poulton, the head fight director for the Specialists, demonstrated his sword-fighting technique with swooshes and stabs. He told the audience that though real swords are dulled for safe stage combat, they still have the potential to do harm.

“Every actor should know how to fall or hold a sword or push someone or throw a punch convincingly, without hurting himself,” Mr. Poulton said, and without being hurt by others.

About half of the attendees were female. “As opposed to set carpenters, which can be very male dominated, props is 50-50,” Mary Gragen, the assistant props master at the George Street Playhouse in New Brunswick, N.J., said. Speculating as to why, she said, “Women multitask very well,” adding, “They are great props artisans and managers because they have to juggle so many balls at the same time.”

When props go awry was a favorite topic of conversation. There was talk of guns that didn’t fire on cue, and doors that didn’t open. Ms. Erdman remembered when an actress in Ferenc Molnar’s farce “The Guardsman” sat on a Victorian settee a little too dramatically at the Berkshire Theater Festival a few years ago.

“The back legs both cracked, and she went head over heels backwards over the sofa,” Ms. Erdman said. “That was kind of bad. The stage manager had to get a milk crate to prop it up for the rest of the show. It’s heartbreaking when furniture breaks onstage.”

The more gratifying part of a props master’s job is constructing one-of-a-kind items. For“Wild With Happy,” the Colman Domingo show coming to the Public next month, Mr. Duckworth is building coffins that transform into cars and park benches.

“We take something ordinary and make it extraordinary,” he said.

Props people have a fierce knack for shopping. Sarah Gill, a properties supervisor for New York University’s graduate theater program, recommends a thrift store on Second Avenue in Murray Hill for “a new set of antiques every week.” For hard-to-find items there’s Pippin Vintage Home, a small store in Chelsea.

“If you need something, you can leave a photo, and they’ll send it to their shoppers upstate,” Ms. Gill said. “If they find something, they’ll buy it for you, and you can buy it from them, which is fabulous.”

A talent for props doesn’t necessarily translate into an eye for interior design or collecting. Ms. Erdman said her home décor was “pretty sparse.”

“I dislike stuff,” she said. “Everything I own fits in my car.”