If you’re making a stage musical of “American Psycho,” one thing’s for sure: There will be blood. But that raises a whole host of questions: How do you make stage blood? How much of it does the show go through each night? And how does the production manage all that plasma on a mostly white set, full of actors clad in vintage 80s couture? In the run-up to the April 21 opening night of show on BroadwayVariety checked in with “American Psycho” director Rupert Goold, SFX specialist Lillis Meeh and theatrical fabric painter Jeff Fender to get answers.

1. The faux plasma is a combination of commercially-made blood, water and soap.
They use a couple of different ratios of blood-to-water in the show, depending on the desired effect and how viscous they want the blood to be. (Straight out of the jug, commercially-made blood is comparable to molasses, Meeh said.) There’s also a soap component, which Meeh likens to ultra-gentle baby shampoo, to help ensure that the mixture is washable and nontoxic. In one of the musical’s bloodiest scenes, they go through about a liter of the stuff each night.

2. “Blood cannons” are an actual thing.
At one point in the show, the musical makes use of compressed-air devices, delightfully called “blood cannons,” to create a splatter effect. In other moments, old-fashioned, low-tech blood pouches are used.

3. The blood on Broadway isn’t the same at the blood London.
As director Goold tells it, the gore in New York’s “American Psycho” is a reimagined version of the more abstract effects used in the original London production, which Goold directed at the Almeida Theater before a West End transfer. (Matt Smith of “Doctor Who” starred in the U.K. staging, while Benjamin Walker steps into the killer role of Patrick Bateman on Broadway.) Goold always wanted to use liquid blood, but was initially put off by the logistical challenges. “We had a real problem. We had a very pristine white set, and very expensive costumes,” he explained. So in London they used a lot of projections — “but it always felt sort of anemic.”

4. When you’re working with blood, sometimes you have to go to some dark places.
Meeh (“Misery,” “Guards at the Taj,” “Let the Right One In”), also a specialist in other stage and screen effects like fire and water, knows a lot more than the average person about how real blood looks and behaves. How’d she acquire that kind of expertise? “It’s just a lot of really depressing Google image searches,” she said with a laugh. (She got into SFX through her father, who was also in the business: “My earliest memory is breaking blood bags into a bathtub.”)

5. Eight bloody performances a week can be murder on costumes.
“American Psycho” drips with references to 80s brand-name clothing, so the costumes are a mixture of throwback designs and real couture dug up from vintage stores. The wear and tear of constant laundering is particularly hard on those vintage duds. One Vivienne Westwood dress in the London staging got particularly ragged, Goold remembered: “Literally by the end of the run it had fallen apart.” But in New York, the production is open to the idea of replacing worn costumes with new vintage finds: “Luckily the shopping for vintage 80s couture is better in New York than it is anywhere else in the world,” the director noted. “So our fall collection in ‘American Psycho’ might be different from our spring one.”

6. Seeing blood spilled on stage is a far different thing from seeing it on screen.
When Goold describes the use of blood in the musical, he delineates four different moods he’s aiming for, ranging from psychological to video game-y. “There’s something very powerful about seeing bloodletting onstage,” he said. “I think it speaks to the fact that the live arts are about a pumping, performing body that’s there in the room with us.”

7. Sometime blood is more than just blood.
“It’s a metaphor, of course,” Goold said — in the case of “American Psycho,” it’s part of the visual language of a razor-sharp satire of 80s-era greed and alienation. “All the media talks about the blood, but really, the show’s more of a musical black hole than it is a slasher,” he said.