The exact blend is a proprietary secret, but this much is revealed: Production of fake vomit begins with 55-gallon drums of natural latex, which resembles thick milk. Colored bits of foam the size of coarse bread crumbs are added: red, yellow, “natural,” two shades of brown, but no green. “Too strong a color,” Putnam said.

“It’s kind of like Grandma’s recipe,” he observed. “A pinch of this, two shakes of that. You kind of know when it’s right.”

The slurry is then ladled onto one Teflon sheet.

The vomitmaster smooths the mixture with the back of the spoon, the way a short-order cook does with pancakes on the griddle. Depending on weather, season and humidity, the pools of fake vomit, 500 to a batch, take overnight to a day and a half to dry. Like snowflakes, no two fake vomits are ever alike, which in the world of manufactured practical jokes is a rare trait.

From an article about the Chicago manufacturer of our fake vomit.