this special method of "photographing" objects is said to be a gateway to the paranormal world of auras. Actually, what is recorded is due to quite natural phenomena such as pressure, electrical grounding, humidity and temperature. Changes in moisture (which may reflect changes in emotions), barometric pressure, and voltage, among other things, will produce different 'auras'.
"Living things...are moist. When the electricity enters the living object, it produces an area of gas ionization around the photographed object, assuming moisture is present on the object. This moisture is transferred from the subject to the emulsion surface of the photographic film and causes an alternation of the electric charge pattern on the film. If a photograph is taken in a vacuum, where no ionized gas is present, no Kirlian image appears. If the Kirlian image were due to some paranormal fundamental living energy field, it should not disappear in a simple vacuum"
(Hines 2003).
There have even been claims of Kirlian photography being able to capture "phantom limbs," e.g., when a leaf is placed on the plate and then torn in half and "photographed," the whole leaf shows up in the picture. This is not due to paranormal forces, however, but to residues left from the initial impression of the whole leaf.