What is Ectoplasm? (And what is it made of?)
Ectoplasm is a substance reportedly spontaneously exuded by the bodies of spirit mediums during ritual events. It can have the appearance, variously, of a liquid, gelatinous mass or length of loosely woven cloth (or some combination thereof).
"Ectoplasm" is also used to describe any fluid or residue thought to indicate the presence of actions of spirits or ghosts. However I an focusing on the more specific application of the term in relation to seances.
Photographs of Examples:
The Paranormal Explanation
Ectoplasm is explained as a complete or partial projection of a spirit into the physical world, presumably for the purpose of sending a message to the living.
The Skeptical Explanation
Mediums have been caught making fake ectoplasm (and even full paper or plastic masks) so it is know, in at least some cases, to be fraudulent. This fraud is also very apparent in some historical photographs where unconvincing apparitions, clearly photographs or paintings, are show ostensibly forming from the ectoplasm.
Ectoplasm is also largely a historical phenomenon linked to spiritualism in the Victorian period and up until the 1930.
It should be noted that the word "ectoplasm" is also used in a purely scientific sense, to refer to the outer layer of a cell (as opposed to the internal "endoplasm").
If there is such as thing as real ectoplasm it is not the unconvincing phlegm photographs in seances. Even experimenters from the hey day of seances who believed ectoplasm was spiritual in natural admitted its appearance was rather absurd.
As ectoplasm is meant to be a real substance, the first step to understanding it would be to determine what it is made of. Samples from the hey-day of spiritualism have proved to be mundane materials. So, so far ectoplasm in the contest of seances seems to be just a hoax.