Filming
Principal photography commenced on August 31, 1970, and ended on November 19, 1970. After location scouting in Europe, including the Guinness brewery in Ireland and a real-life chocolate factory in Spain, production designer Harper Goff decided to house the factory sets and the massive Chocolate Room at Bavaria Studios. It was also significantly cheaper than filming in the United States, and the primary shooting locations in Munich, Bavaria, West Germany were conducive to the desired atmosphere for Wonka's factory. Stuart also liked the ambiguity and unfamiliarity of the location.
External shots of the factory were filmed at the gasworks of Stadtwerke München (Emmy-Noether-Straße 10); the entrance and side buildings still exist as of 2021. The exterior of Charlie Bucket's house, a set constructed solely for the film, was filmed at Quellenstraße in Munich. Charlie's school was filmed at Katholisches Pfarramt St. Sylvester, Biedersteiner Straße 1 in Munich. Bill's Candy Shop was filmed at Lilienstraße, Munich. The closing sequence, in which the Wonkavator is flying above the factory, is footage of Nördlingen, Bavaria and the elevator rising shot showing that it shoots out of the factory was from Bößeneckerstraße 4, 86720 Nördlingen, Germany, now the location of a CAP-Märkte.
The construction of the original Inventing Room was meant to be an industrial room with steel tubes. Stuart envisioned it differently as a wacky inventor's laboratory, with Rube Goldberg-type mechanisms and unusual contraptions and wanted it redesigned to be like Wonka's personality. Goff sent his construction crew into Munich searching junkyards, bakeries and car dealers for discarded machinery, tin funnels, and any other raw materials. This included building Wonka's three-course gum machine, which was originally a solid-state device but Stuart requested an appliance whose operations had a visual experience for the audience. Stuart also instructed Goff to have all the props, furniture and fittings, excluding the light bulbs, in Wonka's original office to be cut in half, to reflect the character's eccentricity. Stuart stated, "I couldn't face the thought of ending the journey through this fabulous factory in an ordinary-looking office."
About a third of the props in the Chocolate Room set were edible. Veruca Salt (Cole) had a chocolate watermelon; Mike Teevee (Themmen) had gum balls from a tree; Violet Beauregarde (Nickerson)'s "three-course gum" was actually a toffee-based candy and marzipan was freely available on set; also there were giant mushrooms filled with whipped cream, and the trees had edible leaves. The inedible items included giant gummy bears that were plastic (the ears were edible, however); the flavored wallpaper was not actually flavored; and Wonka's flower cup was made of wax which Wilder would chew on camera and spit out after each take.
According to Themmen, who played Mike Teevee, "The river was made of water with food coloring. At one point, they poured some cocoa powder into it to try to thicken it but it didn't really work. When asked [what the river was made of], Michael Böllner, who played Augustus Gloop, answers, 'It vas dirty, stinking vater.'" A combination of salt conditioner and some chemicals eventually removed the stink problem but it remained cold, dirty water.
In the scene at Henry Salt (Roy Kinnear)'s peanut factory, where thousands of Wonka bars were being unwrapped to find a Golden Ticket, the bars were actually made of wood, which was a cheaper solution than rewrapping thousands of bars of real chocolate.
For the performances, Stuart used a recurring "method" tactic in a few scenes. When Wonka makes his entrance at the factory gates, nobody was aware of Wilder's approach as he limped then somersaulted; the reaction was of real surprise. The director gave explicit instructions not to allow the child actors to see the Chocolate Room set until the day of the shoot as he wanted their reactions to be genuine. The exception was Julie Dawn Cole, as Goff gave her a sneak preview. Also, the actors were not warned about the tunnel boat ride scene. Similarly, when Wilder rehearsed the Wonka office scene, with Peter Ostrum as Charlie and Jack Albertson as Grandpa Joe, it was in a much calmer tone. When filming started, he increasingly became angry. When he shouted, "So you get nothing!", it was so that the reactions would be authentic.
Stuart had issues with the large size of the Chocolate Room set that caused difficulties lighting the background. Cole's performance of "I Want It Now" as Veruca Salt required 36 takes and was filmed on her thirteenth birthday. Director-choreographer Bob Fosse came in every afternoon to complain because the filming was overrunning towards the end and stopping him from shooting Cabaret (1972) on the same stage.
In addition to the main scenes set in town and at the factory, several comic interludes were also shot. In his book Pure Imagination: The Making of Willy Wonka and the Chocolate Factory, Stuart revealed that his favorite interlude was cut after poor test screenings. In the scene, which took a lot of preparation and money to film, an English explorer climbs a holy mountain to ask a guru the meaning of life. Upon opening a Wonka Bar and finding no Golden Ticket, the guru says, "Life is a disappointment." Stuart loved the scene, but few laughed. He invited a psychologist friend to a preview, where the audience reaction was again muted. The psychologist told him, "You don't understand, Mel. For a great many people, life is a disappointment."
When interviewed for the 30th anniversary special edition in 2001, Wilder stated that he enjoyed working with most of the child actors, but said that he and the film crew had some problems with Themmen. Wilder recalled, "Oh, he was a little brat!" He then addressed Themmen directly, "Now if you're watching this, you know that I love you now, but you were a troublemaker then." An example of Themmen's misbehaviour was releasing bees from a beehive on Wonka's three-course gum machine. Stuart remembered, "As life mirrored one of the morals of the movie, one of the bees stung him."
