The psychical researchers W. W. Baggally and Everard Feilding exposed the British materialization medium Christopher Chambers as a fraud in 1905. A false moustache was discovered in the séance room which he used to fabricate the spirit materializations. The British medium Charles Eldred was exposed as a fraud in 1906. Eldred would sit in a chair in a curtained off area in the room known as a "séance cabinet". Various spirit figures would emerge from the cabinet and move around the séance room, however, it was discovered that the chair had a secret compartment that contained beards, cloths, masks, and wigs that Eldred would dress up in to fake the spirits. https://drive.google.com/file/d/1OnzNdhE1_Mchu77SUdohItnMDlFzN8fJ/view?usp=sharing
In the late 19th century, the fraudulent methods of spirit photographers such as David Duguid and Edward Wyllie were revealed by psychical researchers. Hereward Carrington documented various methods (with diagrams) how the medium would manipulate the plates before, during, and after the séance to produce spirit forms. The ectoplasm materializations of the French medium Eva Carrière were exposed as fraudulent. The fake ectoplasm of Carrière was made of cut-out paper faces from newspapers and magazines on which fold marks could sometimes be seen from the photographs. Cut out faces that she used included Woodrow Wilson, King Ferdinand of Bulgaria, French president Raymond Poincaré and the actress Mona Delza.
Senses used by mental mediums are sometimes defined differently from in other paranormal fields. A medium is said to have psychic abilities but not all psychics function as mediums. The term clairvoyance, for instance, may include seeing spirit and visions instilled by the spirit world. The Parapsychological Association defines "clairvoyance" as information derived directly from an external physical source.