This Tuesday is Halloween, the time of year when we all douse ourselves in fake blood and watch gory movies. But what is that red stuff actually made of, and how has the recipe changed? In 2013, around the release of the new Carrie, Forrest Wickman explored the history of the ever-evolving recipe for fake blood. The post is reprinted below.

When it comes to adaptations of Carrie, the blood literally comes in buckets. For the newest version, director Kimberly Peirce was determined to get the climactic drop of pig’s blood just right. As she described it in a recent New York Times Magazine profile, she tried three-gallon, four-gallon, and five-gallon buckets, and she tried a three-foot drop, a four-foot drop, and a five-foot drop. Trying all these different configurations required take after take after take. When she asked Brian De Palma, director of the classical original Carrie (1976), how many takes it took him, he apparently replied, “What do you mean? We did one.”

Movie gore has come a long way since the first Carrie. What pumps through our veins hasn’t changed a drop, but what goes in those buckets has been reformulated again and again.

Fake movie blood—sometimes called “Kensington Gore,” after the street of that name in London—began evolving long before 1976. For black-and-white films, when blood was permitted at all (the censorship guidelines of the Hays Code in Hollywood didn’t much allow it), filmmakers used something quite simple: chocolate syrup. On black-and-white film, it made a starker contrast than red blood, and no one in the theater would ever know it was just Bosco or Hershey’s.

At first, technical advances were modest. For Psycho (1960), employing state-of-the-art makeup design didn’t mean using a new kind of blood, just a new method of delivery: the plastic squeeze bottle. It was brand new with Shasta chocolate syrup. As makeup supervisor Jack Barron explained it, “This was before the days of the ‘plastic explosion,’ so that was pretty revolutionary. Up to that time in films, we were using Hershey’s, but [with the squeeze bottle] you could do a lot more.”

Color presented new challenges. Starting at least as early as The Curse of Frankenstein (1957), the first color film from the schlockmeisters at Hammer Film Productions—a British studio, exempt from the Hays Code—blood began to splatter the silver screen in Technicolor. But horror filmmakers were still unaccustomed to working in color, and so the blood didn’t look right: In Hammer films like The Curse of Frankenstein and Horror of Dracula (1958), it was cartoonishly bright. The so-called “Godfather of Gore,” Herschell Gordon Lewis, knew this was a problem. While working on what became the first splatter film, Blood Feast (1963), he “realized how purple the fake blood at that time was because it had been prepared for black-and-white movies.” To avoid using these substandard materials, he got his blood custom, from the charmingly named Barfred Laboratories.

The bright red blood wasn’t a problem for everyone. Jean-Luc Godard used a bright, unnaturalistic red for movies like Pierrot Le Fou (1965). This suited Godard’s more abstract, self-conscious approach to the movies. When Cahiers du cinema pointed out, “There’s a good deal of blood in Pierrot,” Godard shot back: “Not blood, red.”

But the man who revolutionized movie blood—and the rest of movie makeup—was Dick Smith. For groundbreaking and bloodletting movies like The Godfather (1972), The Exorcist (1973), and Taxi Driver (1976), Smith perfected the recipe for fake movie blood:

1 quart white corn syrup

1 level teaspoon methyl paraben

2 ounces Ehlers red food coloring

5 teaspoons Ehlers yellow food coloring

2 ounces Kodak Photo-Flo (Poisonous)

The corn syrup served as the base, the methyl paraben served as a preservative for longer shoots, the food coloring was adjusted for just the right hue, and the Photo-Flo made sure the red stuff flowed just right—it ran over skin and soaked into fabric just like real blood.

In fact, the new blood quickly proved a little too real. When the Motion Picture Association of America (MPAA) got its hands on Taxi Driver and its climactic bloodbath, they threatened it with an X rating. Columbia Pictures told director Martin Scorsese that if he didn’t recut the movie to an R, which would mean hacking away at the finale, they would do it for him. Scorsese came up with a solution: In order to make the blood look less realistic, he desaturated its color until it took on more of a sepia tone. Scorsese has said that he secretly thought the new blood was even more disturbing, but the MPAA gave the movie an R.

Today there are dozens of different recipes for movie blood, though many are simple variations on Dick Smith’s formula. For edible blood—essential if the fake blood might get in the actor’s mouth, or if a scene requires that the actor cough it up—there are recipes for “Chocolate Blood” and “Peanut Butter Blood.” For Evil Dead fans, there’s Bruce Campbell’s recipe for another edible blood, which uses nondairy creamer. For those who don’t want to do the work of making the blood themselves, fake blood for movies is also available commercially: Robert Benevides, who teaches special effects makeup at New York University’s Tisch School, told me that the best blood today is an alcohol-based blood called Fleet Street Bloodworks, which retails at $65 per pint.

Often several different kinds of blood are used for the same movie. In addition to whether the blood is edible, each blood is selected according to the lighting, whether the blood should slowly dry or stay wet, whether it’s arterial (lighter) or venous (darker), and what kind of style the director is looking for. For one of his gorier plays, writer-director Martin McDonagh used nine distinct varieties of fake blood. And some filmmakers still want the old-fashioned stuff: For the nightclub massacre in Kill Bill, Vol. 1 (2003), Quentin Tarantino ordered more than 100 gallons of “samurai blood.” “I’m really particular about the blood, so we’re using a mixture depending on the scenes,” he explained. “I say, ‘I don’t want horror movie blood, all right? I want Samurai blood.’ … You have to have this special kind of blood that you only see in Samurai movies.”

The newest fake blood isn’t made out of chocolate syrup or nondairy creamer: It’s made out of pixels. This computer-generated blood has been used not just for horror movies and schlocky action flicks like The Expendables 2 (for which all the blood was CGI), but for key sequences in movies like David Fincher’s Zodiac (2007) and Michael Mann’s Public Enemies (2009). The CGI blood allowed Mann to show a bullet exiting John Dillinger’s cheek without having to cover Johnny Depp’s face in prosthetics. Fincher reportedly preferred CGI blood because it allowed him to shoot many takes without having to wait around between each one for setup and cleanup.

But both CGI blood and the practical stuff have their shortcomings. For the original Carrie, a combination of Karo syrup and food coloring looked great, but it was “sticky,” star Sissy Spacek later recalled: “When they lit the fires behind me to burn down the gym,” she said, “I started to feel like a candy apple.” (Bruce Campbell has had similar issues: At one point during the making of Evil Dead, his shirt hardened and “broke.”) For the new Carrie, CGI blood was reportedly used for some scenes, angering fans that have complained that it looks fake. These fans may be worried that CGI blood is replacing all practical makeup, but, according to effects coordinator Warren Appleby, the old-fashioned stuff is still very much alive: He and his crew used “upwards of 300, 400 gallons … just for the iconic blood drop.”