In June 1972, Sabbath began work on their fourth album at the Record Plant studios in Los Angeles.
"It's the first album we've produced ourselves," observed Ozzy Osbourne. "Previously we had Rodger Bain as a producer – and, although he's very good, he didn't really feel what the band was doing. It was a matter of communication. This time, we did it with Patrick, our manager, and I think we're all very happy… It was great to work in an American studio."
The recording was plagued with problems, many due to substance abuse. In the studio, the band regularly had speaker boxes full of cocaine delivered.
Struggling to record "Cornucopia" after "sitting in the middle of the room, just doing drugs", Bill Ward feared that he was to be fired: "I hated the song, there were some patterns that were just horrible. I nailed it in the end, but the reaction I got was the cold shoulder from everybody. It was like 'Well, just go home, you're not being of any use right now.' I felt like I'd blown it, I was about to get fired." According to the book How Black Was Our Sabbath, Ward "was always a drinker, but rarely appeared drunk. Retrospectively, that might have been a danger sign. Now, his self-control was clearly slipping." Iommi claims in his autobiography that Ward almost died after a prank-gone-wrong during recording. The Bel Air mansion the band was renting belonged to John du Pont and the band found several spray cans of gold DuPont paint in a room of the house; finding Ward naked and unconscious after drinking heavily, they proceeded to cover the drummer in gold paint from head to toe. According to Sharon Osbourne's memoirs, a Doberman at the mansion got into part of the band's cocaine supply, laced with the baby laxative mannitol, and became ill from the effects of the drug.
The Vol. 4 sessions could be viewed as the point when the seeds were planted for the demise of Sabbath's classic line-up. Bassist Geezer Butler told Guitar World in 2001: "The cocaine had set in. We went out to L.A. and got into a totally different lifestyle. Half the budget went on the coke and the other half went to seeing how long we could stay in the studio ... We rented a house in Bel Air and the debauchery up there was just unbelievable." In the same interview, Ward said: "Vol. 4 is a great album, but listening to it now, I can see it as a turning point for me, where the alcohol and drugs stopped being fun." To Guitar World in 1992, Iommi admitted, "LA was a real distraction for us, and that album ended up sounding a bit strange. The people who were involved with the record really didn't have a clue. They were all learning with us, and we didn’t know what we were doing either. The experimental stage we began with Master of Reality continued with Vol. 4, and we were trying to widen our sound and break out of the bag everyone had put us into." In the liner notes to 1998's Reunion, Iommi reflected, "By the time we got to Bel Air we were totally gone. It really was a case of wine, women and song, and we were doing more drugs than ever before." In his memoir Iron Man: My Journey Through Heaven & Hell with Black Sabbath, the guitarist says, "Like Tony Montana in the movie Scarface: we'd put a big pile (of cocaine) on the table, carve it all up and then we'd all have a bit, well, quite a lot."
In his autobiography I Am Ozzy, Osbourne speaks at length about the sessions: "In spite of all the arsing around, musically those few weeks in Bel Air were the strongest we'd ever been." But he admits, "Eventually we started to wonder where the fuck all the coke was coming from ... that coke was the whitest, purest, strongest stuff you could ever imagine. One sniff, and you were king of the universe." Osbourne also recounts the band's ongoing anxiety over the possibility of being busted, which worsened after they went to the cinema to see The French Connection (1971), about undercover New York City cops busting an international heroin-smuggling ring. "By the time the credits rolled," Osbourne recalled, "I was hyperventilating." In 2013, Butler admitted to Mojo magazine that heroin, too, had entered the picture: "We sniffed it, we never shot up ... I didn't realize how nuts things had gotten until I went home and the girl I was with didn't recognize me."