In the 1930s Harry Price (director of the National Laboratory of Psychical Research) had investigated the medium Helen Duncan and had her perform a number of test séances. She was suspected of swallowing cheesecloth which was then regurgitated as "ectoplasm".[151] Price had proven through analysis of a sample of ectoplasm produced by Duncan, that it was made of cheesecloth.[152] Helen Duncan would also use a doll made of a painted papier-mâché mask draped in an old sheet which she pretended to her sitters was a spirit.[153] The photographs taken by Thomas Glendenning Hamilton in the 1930s of ectoplasm reveal the substance to be made of tissue paper and magazine cut-outs of people. The famous photograph taken by Hamilton of the medium Mary Ann Marshall depicts tissue paper with a cut out of Arthur Conan Doyle's head from a newspaper. Skeptics have suspected that Hamilton may have been behind the hoax.[154]
Magicians have a long history of exposing the fraudulent methods of mediumship. Early debunkers included Chung Ling Soo, Henry Evans and Julien Proskauer.[62] Later magicians to reveal fraud were Joseph Dunninger, Harry Houdini and Joseph Rinn. Rose Mackenberg, a private investigator who worked with Houdini during the 1920s, was among the most prominent debunkers of psychic fraud during the mid-20th century.[63]
^ "Glossary of Key Words Frequently Used in Parapsychology" Archived 2010-12-24 at the Wayback Machine, Parapsychological Association website. "Materialization: A phenomenon of physical mediumship in which living entities or inanimate objects are caused to take form, sometimes from ectoplasm." Retrieved January 24, 2006 "Medium – Definition". Retrieved 23 March 2007.