From its earliest beginnings to contemporary times, mediumship practices have had many instances of fraud and trickery. Séances take place in darkness so the poor lighting conditions can become an easy opportunity for fraud. Physical mediumship that has been investigated by scientists has been discovered to be the result of deception and trickery. Ectoplasm, a supposed paranormal substance, was revealed to have been made from cheesecloth, butter, muslin, and cloth. Mediums would also stick cut-out faces from magazines and newspapers onto cloth or on other props and use plastic dolls in their séances to pretend to their audiences spirits were contacting them. Lewis Spence in his book An Encyclopaedia of Occultism (1960) wrote:
In 1925, Samuel Soal claimed to have taken part in a series of séances with the medium Blanche Cooper who contacted the spirit of a soldier Gordon Davis and revealed the house that he had lived in. Researchers later discovered fraud as the séances had taken place in 1922, not 1925. The magician and paranormal investigator Bob Couttie revealed that Davis was alive, Soal lived close to him and had altered the records of the sittings after checking out the house. Soal's co-workers knew that he had fiddled the results but were kept quiet with threats of libel suits.
Skeptics have challenged the veracity of the claims of psychic readings, largely through disclosure of the methods. Psychologist Richard Wiseman's 2011 book Paranormality: Why We See What Isn't There noted the tricks of the trade, and Wiseman noted in a podcast appearance that the disclosure generated negative feedback from the psychic community.
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.