Another theory on the image formation is corona discharge/electrostatic discharge. Guilio Fanti is a proponent of this.
After a presentation of the main points regarding CD (Corona Discharge), and the definition of the hypotheses regarding the assumed model, some new evidence is presented and discussed here, such as the exsiccation of limited parts of linen fibers. The paper then explains different points raised by the SSG, such as the radiation direction, the 3-D effects of radiation and its mathematical representation, the image resolution, the double draping configurations of the TS, and the color on the linen fibers.The experimental results obtained to support the hypothesized mechanism show no appreciable chemical-physical differences from the image features of the TS. These results confirm that the proposed CD mechanism could have been involved in the TS body image formation.
https://www.shroud.com/pdfs/ohiofanti1.pdf
What is corona discharge?
A Corona Discharge (CD) is an electrical discharge (Chen J., 2002) brought on by the ionization of a fluid surrounding a conductor which occurs when the potential gradient exceeds a threshold in situations where sparking is not favored. In a CD, a current develops between two high-voltage electrodes in a dielectric fluid, usually air, by ionizing the fluid so as to generate a plasma (which is the fourth state of matter beyond solid, liquid and gas) around one electrode. This leads to the collection of electrons and ions made by stripping the electrons from atoms and electronic emission from the negatively polarized electrode. The ions generated are used as the charge carriers to the other electrode. CD usually involves two asymmetric electrodes, one highly curved (emitter, injector or active conductor) and one of low curvature (collector).
https://www.shroud.com/pdfs/ohiofanti1.pdf
It is the UV light and heating from a corona discharge that would be causing the image formation.
Heating (from about 50 °C to 150 °C) and UV luminescence are probably the two most important effects for the body image formation because they could be responsible for the polysaccharides dehydrating of the linen cloth. Although electrons are the medium that triggers the process, it is the UV light and heating that produce the image: they react with the linen fibers, and break their C=C chemical compounds. This is what can almost be interpreted from experimental tests done using a plasma ball.
https://www.shroud.com/pdfs/ohiofanti1.pdf
An electric field is proposed that is generated from the body and electrons move through regular electric field lines to the cloth. The author readily admits there is no naturalistic explanation how this can happen. As we see in plasma balls, electric discharges from the inner electrode to the outer glass do not result in a regular uniform path.
The corona discharge has some ability to explain the coloring of the fibers, but it doesn’t go much beyond that. It is not a comprehensive explanation of the entire shroud. So, it shares several of the same weaknesses of the Maillard reaction theory.
It does not explain the head gap, depth encoding, angle encoding, x-ray effect, second degree distortions, unbroken blood stains, and uncolored fibers adjacent to colored fibers.
https://debatingchristianity.com/forum/viewtopic.php?p=1124174#p1124174