Kirlian's work, from 1939 onward, involved an independent rediscovery of a phenomenon and technique variously called "electrography," "electrophotography," and "corona discharge photography." The Kirlian technique is contact photography, in which the subject is in direct contact with a film placed upon a metal plate charged with high voltage, high frequency electricity.
The underlying physics (which makes xerographic copying possible) was explored as early as 1777 by Georg Christoph Lichtenberg (see Lichtenberg figures). Later workers in the field included Nikola Tesla; various other individuals explored the effect in the later 19th and early 20th centuries.
Kirlian made controversial claims that the image he was studying might be compared with the human aura. An experiment advanced as evidence of energy fields generated by living entities involves taking Kirlian contact photographs of a picked leaf at set periods, its gradual withering being said to correspond with a decline in the strength of the aura. However it may simply be that the leaf loses moisture and becomes less electrically conductive, causing a gradual weakening of the electrical field at the drier edges of the leaf. However, leaves that were partially cut off would continue to display the Kirlian outlines of the missing part for sometime. The Journal of the Smithsonian Institute published a leading article with reproductions of images of this phenomenon. According to James Randi's online An Encyclopedia of Claims, Frauds, and Hoaxes of the Occult and Supernatural, "Since the same glass plates had been used, it is believed that moisture from the missing portion was providing the ghostly image."
In addition to living material, inanimate objects such as coins will also produce images on the film in a Kirlian photograph setup. In the United States, Dr. Thelma Moss of UCLA devoted much time and energy to the study of Kirlian photography when she led the parapsychology laboratory there in the 1970s. Much of her time was devoted to efforts to avoid factors proposed by skeptical peer-review.
Current research continues by Dr. Konstantin Korotkov in the Russian University, St.Petersburg State Technical University of Informational Technologies, Mechanics and Optics. Dr. Korotkov has published several books. He uses GDV (Gas Discharge Visualization) based on the Kirlian Effect. GDV instruments use glass electrodes to create a pulsed electrical field excitation (called "perturbation technique") to measure electro-photonic glow.
The Korotkov methods are used in some hospitals and athletic training programs in Russia and elsewhere as preventative measurements for detecting stress. The Russian Academy of Science has approved the GDV techniques and equipment in 1999 for general clinical use, though it should be noted that the "approval", according to the certificates Dr. Korotkov himself is showing in his various web sites, only covers conformity with general electrical safety (standards 61010 and 61326).
The accepted physical explanation is that the images produced are those typically caused by a high voltage corona effect, similar to those seen from other high voltage sources such as the Van de Graaff generator or Tesla coil. In a darkened room, this is visible as a faint glow but, because of the high voltages, the film is affected in a slightly different way from the usual. Color photographic film is calibrated to faithfully produce colors when exposed to normal light. The corona discharge has a somewhat different effect on the different layers of dye used to accomplish this result, resulting in various colors depending on the local intensity of the discharge.