Yes, that's definitely one disgusting special effect.
Due to my participation in a production of this play with the puking, I can verify that even making vomit sounds is unsettling to an audience. But if you do a full-blown production, so to speak, you need special vomit tech. Here's the meat of Jessica Goldstein's article from The Washington Post:
In Signature Theatre’s production of “God of Carnage” by Yasmina Reza, actress Vanessa Lock’s character, with husband in tow, is trying to apologize to another couple whose child her son punched on the playground. About 15 minutes into the performance at the Arlington theater, Lock throws up all over the victim’s parents’ living room.Note: If for some reason you're still interested in throwing up and deception, you may search for "vomit" on this site for additional stories of regurgitation.
At ease, front-row ticketholders: It is not real puke! It is a concoction created by Aly Geisler, prop master. Geisler reveals her secret cocktail: two baby food containers of peas, four cups of water and a half-serving of oatmeal.
In case you are wondering how such a feat is accomplished, one garden-hose-type tube runs from a pressurized tank behind the scenery up the back of a skintight bodysuit Lock wears beneath her costume. The tube ends right at Lock’s wrist and comes pre-loaded with oatmeal.
“We started with cream of wheat, but it was too viscous,” explained Geisler. “Our electric valve didn’t have enough power to turn it off. It was like a waterfall of never-ending vomit.”
Why don’t you work on that visual for a second while Lock describes the purpose this serves in the plot? “I think what that does is it frees up all four of us. It pushes us into another relationship, because I’ve exposed so much of myself,” she said. “I sort of vomit all that out and, okay, now we’re going to show who we really are.”
Back to the engineering: Lock, all juiced up with the oatmeal tube, sits on the couch and plugs herself into a hidden tube in the sofa. This tube is connected to the tank at one end and the couch cushion at the other. When Lock flips a switch, Geisler said, “the air and peas go rushing through. The peas come forward, and the force of that pushes the oatmeal and the peas out.”
Lock insists that “the ‘ick’ factor” is more on her castmates than on her; she gets to run offstage and wash her face while they’re left to mop up the mess. Though this is not to suggest she emerged from the experience unscathed: “I like pea soup,” she said. “But I don’t know that I’ll eat pea soup again anytime soon.”
Projectile puking plays leading role in Signature’s ‘God of Carnage’, Washington Post>>
Found via Book of Joe>>