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".[148] Price had proven through analysis of a sample of ectoplasm produced by Duncan, that it was made of cheesecloth.[149] 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.[150] 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.[151]
In 1907, Hereward Carrington exposed the tricks of fraudulent mediums such as those used in slate-writing, table-turning, trumpet mediumship, materializations, sealed-letter reading and spirit photography.[107] between 1908 and 1914 the Italian medium Francesco Carancini was investigated by psychical researchers and they discovered that he used phosphorus matches to produce "spirit lights" and with a freed hand would move objects in the séance room.[108]

In September 1878 the British medium Charles Williams and his fellow-medium at the time, A. Rita, were detected in trickery at Amsterdam. During the séance a materialized spirit was seized and found to be Rita and a bottle of phosphorus oil, muslin and a false beard were found amongst the two mediums.[82] In 1882 C. E. Wood was exposed in a séance in Peterborough. Her Indian spirit control "Pocka" was found to be the medium on her knees, covered in muslin.[83]