What is the evidence?
Sadly, since we cannot prove the existence of ghosts in a laboratory (in spite of some truly ingenious efforts to do so – please read Mary Roach's excellent book Spook), the only evidence we have for any phenomena in the séance room is anecdotal.
Certainly there are records of hundreds of investigations of purported mediums, many of whom were supposedly able to produce ectoplasm. However, even among those few where obvious trickery was not discovered immediately by the investigators, little to no work has been done in examining the actual functioning of the ectoplasm in order to allow movements, levitations, or physical contacts of any other sort.
With one very important exception.
Possibly the
most important book on the subject, written by a professor of
Mechanical Engineering who actually witnessed the movement of a
table at repeated visits to an amateur spirit medium (this is
the person who facilitates the séance, including exuding the
ectoplasm for spirit use) was published in 1921 by William J.
Crawford. The Psychic Structures at the Goligher Circle
details the physical forms that Crawford hypothesized must have
been shaped from the ectoplasm (which he accepted as real) in
order to lift and tilt the table of the medium Kathleen Goligher
during séances which Crawford attended. His engineering
knowledge was applied to the problem of how the structures must
function in order to allow the spirit “operators” to lift the
table in the middle of the séance circle.
He later verified the accuracy of these hypothetical structures by asking the spirits to either confirm or deny his ideas about the forms of levers and cantilevers formed by the ectoplasm. The spirits confirmed him in every detail.
For a brief, very clear, and cogent overview of the role of Miss Goligher as spirit medium, see the Wikipedia article: https://en.wikipedia.org/wiki/Kathleen_Goligher
For the purposes of this project, I am not trying to either prove or debunk any point of view as regards spirits and their séance antics. I just wish to compare the structures Crawford believed were used by said spirits to some known or suggested alternative methods of achieving the same results.
But first I needed Crawford's book.
I had expected to frustrate the librarians in the interlibrary loan office by asking for such an obscure book as a century-old exhaustive explanation of Goligher's ectoplasmic cantilevers, but it turns out that some kind souls have made the entire tome freely available for those who wish to investigate such subjects in detail. https://archive.org/details/psychicstructure00craw will take you there.
While there were and are many other mediums, some quite a bit more famous than Miss Goligher ever was, I chose to concentrate on the events of the Goligher circle rather than any others because the Goligher manifestations are the only example I have ever seen or heard of in which an engineer attempted to determine the actual structure of the ectoplasm as it formed rigid (though remarkably temporary) members to do the amazing things that it seems to have done.
Read on, if
you dare!