Between 8 November and 31 December 1920 Gustav Geley of the Institute Metapsychique International attended fourteen séances with the medium Franek Kluski in Paris. A bowl of hot paraffin was placed in the room and according to Kluski spirits dipped their limbs into the paraffin and then into a bath of water to materialize. Three other series of séances were held in Warsaw in Kluski's own apartment, these took place over a period of three years. Kluski was not searched in any of the séances. Photographs of the molds were obtained during the four series of experiments and were published by Geley in 1924. Harry Houdini replicated the Kluski materialization moulds by using his hands and a bowl of hot paraffin.
Ray Hyman discovered many methodological errors with Schwartz's research including; "Inappropriate control comparisons", "Failure to use double-blind procedures", "Creating non-falsifiable outcomes by reinterpreting failures as successes" and "Failure to independently check on facts the sitters endorsed as true". Hyman wrote "Even if the research program were not compromised by these defects, the claims being made would require replication by independent investigators." Hyman criticizes Schwartz's decision to publish his results without gathering "evidence for their hypothesis that would meet generally accepted scientific criteria... they have lost credibility."
The medium Frank Decker was exposed as a fraud in 1932. A magician and séance sitter who called himself M. Taylor presented a mail bag and Decker agreed to lock himself inside it. During the séance objects were moved around the room and it was claimed spirits had released Decker from the bag. It was later discovered to have been a trick as Martin Sunshine, a magic dealer admitted that he sold Decker a trick mail bag, such as stage escapologists use, and had acted as the medium's confederate by pretending to be M. Taylor, a magician. The British medium Estelle Roberts claimed to materialize an Indian spirit guide called "Red Cloud". Researcher Melvin Harris who examined some photographs of Red Cloud wrote the face was the same as Roberts and she had dressed up in a feathered war-bonnet.
In the late 1920s and early 1930s there were around one quarter of a million practising Spiritualists and some two thousand Spiritualist societies in the UK in addition to flourishing microcultures of platform mediumship and 'home circles'. Spiritualism continues to be practised, primarily through various denominational Spiritualist churches in the United States, Canada, Australia and the United Kingdom. In the United Kingdom, over 340 Spiritualist churches and centres open their doors to the public and free demonstrations of mediumship are regularly performed.