The medium Henry Slade was caught in fraud many times throughout his career. In a séance in 1876 in London Ray Lankester and Bryan Donkin snatched his slate before the "spirit" message was supposed to be written, and found the writing already there. Slade also played an accordion with one hand under the table and claimed spirits would play it. The magician Chung Ling Soo revealed how Slade had performed the trick.
The psychical researchers Eric Dingwall and Harry Price re-published an anonymous work written by a former medium entitled Revelations of a Spirit Medium (1922) which exposed the tricks of mediumship and the fraudulent methods of producing "spirit hands". Originally all the copies of the book were bought up by spiritualists and deliberately destroyed. In 1923, the magician Carlos María de Heredia revealed how fake spirit hands could be made by using a rubber glove, paraffin and a jar of cold water.
In 1917, Edward Clodd analyzed the mediumship of the trance medium Gladys Osborne Leonard and came to the conclusion that Leonard had known her séance sitters before she had held the séances, and could have easily obtained such information by natural means. The British psychiatrist Charles Arthur Mercier wrote in his book Spiritualism and Sir Oliver Lodge (1917) that Oliver Lodge had been duped into believing mediumship by trickery and his spiritualist views were based on assumptions and not scientific evidence. https://drive.google.com/file/d/1Zh3T7RuksHd5otikwphwAW6hgGTlHjfr/view?usp=sharing
^ "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". Dictionary.com. Retrieved 23 March 2007.