Slate-writing is the appearance of writing on a blank slate, allegedly through the intervention of the spirits. Slate-writing also is called psychography. Unlike most other mediumistic phenomena, slatewriting seemed to offer many early Spiritualists irrefutable proof of spirit presence.

The SĂ©ance could be held in full light, conditions presented ample opportunity to guard against fraud, and most sittings produced results. Many believers testified that as they watched the medium the entire time, chicanery was impossible. However, trickery was often employed. Students no longer use slates for schoolwork, but in the 19th century they were a common tool and were available everywhere.

Slates came in single or double, hinged models, usually framed; the double slates could be latched. Sitters often brought their own new, clean slates to the SĂ©ance, locked and sealed, and were amazed to find the blank surfaces covered with writing by the spirits.

A slate-writing Séance usually proceeded as follows: after the slates had been thoroughly washed and examined, a sitter would ask a question aloud, or, to be even more secretive, would seal a question in an envelope. The medium would then hold the slate at one end underneath the tabletop with the fingers of his right hand and would keep his thumb above the table. The sitter would hold the other end with one hand and grasp the medium’s left hand with his or her other one.

In this rather awkward position it was difficult for the sitter to observe the slate or the medium’s fi ngers under the table. Soon, scratchy writing sounds would be heard, followed by two or three raps when the spirits were finished. And there would appear the answer, even to the sealed question. A variation of slate-writing perfected by Kate Fox (see Fox Sisters) was called “mirror-writing”; the Medium wrote backward on the slate and held it up to a mirror to read.

Another manifestation produced pictures on the slates instead of words. The most famous slate-writer was “Dr.” HENRY SLADE. He conducted Séances in New York for 15 years before receiving the endorsement of Madame Helena Petrovna Blavatsky and her associate, Colonel Henry Steel Olcott, the cofounders of the Theosophical Society. Olcott recommended Slade for study at the University of St. Petersburg in Russia.

En route to St. Petersburg in July 1876, he stopped in London to introduce the British to slate-writing. Several scientists and scholars found no indications of trickery and left Slade’s Séances convinced of supernormal agencies. He was later exposed as a fraud, however, by Prof. E. Ray Lankester and Dr. Horatio B. Donkin and was convicted of taking money under false pretenses.

The conviction was overturned on a technicality and Slade rapidly left England. His career continued for a few years, but he lost his place of supremacy to William Eglinton and Dr. Francis Ward Monck, who also were later suspected of fraud. One member of the Society for Psychical Research (SPR), S.J. Davey, became so adept at reproducing Slade’s effects that he held Séances himself. Although he never tried to pass himself off as a medium, even sitters who knew he conjured the writing still believed the spirits had had a hand.

Magicians such as J. N. Maskelyne and Harry Houdini showed the public that there were two basic ways of producing the slate-writing phenomena. The first was to attach a tiny bit of slate pencil to a ring on one of the fingers holding the slate under the table and use it to scratch out an answer.

Once the answer had been written, the medium would suffer a nervous spasm, or a coughing spell—anything to divert the sitter’s attention—and deftly fl ip the slate over, so that it appeared the writing had formed on the side up under the tabletop. The writing was understandably crude and often illegible. Some mediums even learned how to write with their feet.

The other method involved writing out the answer beforehand and switching the slates while the sitter’s attention was again diverted. The substitute could be hidden on the medium’s person or in or near the furniture or could even be provided by a confederate from another room.

Often the SĂ©ance would be interrupted by a knock at the door, and the medium would rise to answer a seemingly unrelated question. Slates would be surreptitiously switched before the medium returned. Too often the sitter was so completely bowled over that this interruption was overlooked. Penmanship vastly improved with this technique.

Another method involved writing the message beforehand and concealing it with a flap of silicated gauze, or thin slate. One side of the flap is covered with fabric to match the table covering, and when laid down is not noticed. An even better method was to use newspaper and drop the pre-written slate on another newspaper, where it would be camouflaged.

Trick slates and manipulation of the hinge mechanisms allowed proficient slate-writing mediums to produce writing on the inside surfaces of a locked double slate. If the medium was a good talker, he could switch slates even over a sitter’s head without his or her knowledge.

Other mediums used confederates to read the questions and provide the answers, then make the switch. A few employed trap panels or trap doors in the SĂ©ance room for the assistants to use. Especially talented slatewriting mediums prepared their slate pencils with iron fi lings, then used a magnet to pull the pencil and write backwards.

This technique necessitated using a mirror as Kate Fox had done. To draw pictures on the slates, the medium covered the entire slate with slate pencil or chalk, rubbing lightly until the surface was white. Then pictures cut from magazines or newspapers (it was suggested to leave about a 1-inch margin around the lines) were wet and laid on the powdered surface.

Taking a pencil, the medium traced Harry Houdini’s sketch showing how Henry Slade allegedly did his slate-writing. The lines of the picture, allowed the paper to dry and then removed it, leaving an excellent impression. As for the sealed questions and slates provided by the sitters, a talented medium could insert a tiny wire prong in the small unsealed part of an envelope, twirl the wire and pull the message out through the opening, read it and return it.

The envelope remained sealed. And since slates were so commonplace, most mediums kept a supply of all the available types, ready to replace in any situation. Finally, if the slate-writing medium needed more help than he could devise on his own, firms such as the Ralph E. Sylvestre Co. in Chicago offered trick slates of all types through a mail-order catalogue entitled “Gambols With the Ghosts.”



  • Cannell, J. C. The Secrets of Houdini. New York: Bell Publishing Co., 1989.
  • Douglas, Alfred. Extra-Sensory Powers: A Century of Psychical Research. Woodstock, N.Y.: The Overlook Press, 1976.
  • Doyle, Sir Arthur Conan. The History of Spiritualism Vol. I & II. New York: Arno Press, 1975.
  • Houdini, Harry. Houdini: A Magician Among the Spirits. New York: Arno Press, 1972.
  • Oppenheim, Janet. The Other World: Spiritualism and Psychical Research in England 1850–1914. New York: Cambridge University Press, 1985.
  • Podmore, Frank. Mediums of the Nineteenth Century. New Hyde Park, N.Y.: University Books, 1963. First published as Modern Spiritualism, London, 1902.


The Encyclopedia of Ghosts and Spirits– Written by Rosemary Ellen Guiley – September 1, 2007