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Special effects, makeup and costumes

Arnold Gillespie, the film's special effects director, employed several techniques. Developing the tornado scene was especially costly. Gillespie used muslin cloth to make the tornado flexible, after a previous attempt with rubber failed. He hung the 35 ft (11 m) of muslin from a steel gantry and connected the bottom to a rod. By moving the gantry and rod, he was able to create the illusion of a tornado moving across the stage. Fuller's earth was sprayed from both the top and bottom using compressed air hoses to complete the effect. Dorothy's house was recreated using a model. Stock footage of this tornado was later recycled for a climactic scene in the 1943 musical film Cabin in the Sky, directed by Judy Garland's eventual second husband Vincente Minnelli.

The Cowardly Lion and Scarecrow masks were made of foam latex makeup created by makeup artist Jack Dawn. Dawn was one of the first to use this technique. It took an hour each day to slowly peel Bolger's glued-on mask from his face, a process that eventually left permanent lines around his mouth and chin.

The Tin Man's costume was made of leather-covered buckram, and the oil used to grease his joints was made from chocolate syrup. The Cowardly Lion's costume was made from real lion skin and fur. Due to the heavy makeup, Bert Lahr could only consume soup and milkshakes on break, which eventually made him sick. After a few months, Lahr put his foot down and requested normal meals along with makeup redos after lunch. For the "horse of a different color" scene, Jell-O powder was used to color the white horses. Asbestos was used to achieve some of the special effects, such as the witch's burning broomstick and the fake snow that covers Dorothy as she sleeps in the field of poppies.