Investigation into the luminescent effects of high voltage on pickled foodstuffs.

As seen in the national press.



A scientific investigation into the luminescent properties of a small variety of pickled vegetables when a large alternating voltage is applied across them. The differences between pickled gherkins and pickled onions as well as the effects of the separation of the electrodes are investigated.

The aim was to test the hypothesis put forward by John Hall that pickled onions and gherkins glow when a mains current is passed through them.

Apparatus Used

Equipment Used

The equipment consisted of a length of 2 core cable with a 13A plug on one end and two electrodes on the other, initially made from pop rivets but substituted at an early stage for straightened paper clips. A 5A fuse was fitted on the extension cord used to set a maximum current, Imax, that could be passed through the test subject. An RCD was used at the interface of the extension wire and the wire with the electrodes at the end. See the Circuit Diagram.

The experiments were carried out on the balcony which had a strip of lead running around the low parapet against which the apparatus was placed. It was therefore desirable to tape an A4 file against the wall to insulate the lead. The file was clearly labelled with an orientation indicator to prevent human error. The wire was taped to this file with the electrodes hanging down in front of it above a plate where the subjects were placed. A plate was considered inert enough to withstand the inevitable leakage of preservative from the subject.

The Apparatus

The electrodes were inserted at the extremes of the subject for the initial experiments to maximise the resistance between the electrodes. The control subjects were left on a plate inside.


As well as being a convenient switch, the RCD guarded against the possibility of the subject accidentally being connected to earth while live. The parapet ensured that any passing civilians would not be injured by any blast that occurred. Additionally, th e operators could utilise the patio window opening onto the balcony as a blast shield for themselves.

The wire running across the balcony was carefully taped down to avoid accidents to any of the experimenters during the experiments. The positions of nearby H2O and CO2 fire extinguishers were also noted. The H2O was purely in case any of the surroundings caught fire and was only to be used once all power had been cut.

Typical Techie Safety Precautions Atypical Techie Safety Precautions

The resistance across the pins of the 13A plug was measured before each experiment to ensure that Imax was not exceeded. However, as it turned out later, was not a sufficient test.

Measuring the resistance of the subject


Initial experiments with gherkins were a little disappointing; they did glow but only in a localized area around one electrode. Decreasing the separation of the electrodes did produce better results but the effect was still only at one end. There was also a crackling noise and some smoke/steam from around the active electrode; no quantitative measurements were made of this.

Pickled onions were a lot more interesting and it was these that were concentrated upon during the latter experiments. The luminescence and sound caused by the vibration of the electrode were more intense. It was noticed during these experiments that the active electrode tended to move and cut through the subject as it drifted unerringly towards the other electrode - a process known as Electrode Drift (E.D.). This curtailed the possible length of many of the experiments, because contact of the electrodes was deemed to be a Bad Thing™.

Here we see a classic example of E.D. "tramlines" in a pickled onion:

Electrode Drift

It was noticed during the experiment, that the resistance we were measuring was actually being registered as negative much to the researchers' consternation as well as arousing their curiosity. Setting the multimeter to measure dc and putting it across th e an onion (not while it was live) a discernible voltage was measured of about 0.24 Volts.

The potential difference measured across the subject

An interesting effect that was noted, was that it was not around the same electrode that the reaction happened each time, and their are examples in the results that show that the reaction could occur at either the live or the ne utral electrode. It seems that once the reaction has started at one of the electrodes then it seems to continue at that point. There was one experiment where it was observed that the reaction started at one, stopped, and then started at the other. This be haviour was subsequently unable to be produced. An explanation has been provided by Dr. Robin Ball, a physicist at the Cavendish Laboratory, Cambridge for this phenomenon.

The control subjects did not luminesce or smoke or make any sound.; in fact there was no change in them at all*.

Click here to see pictures of the results

* with apologies to the T.W.I.N.K.I.E.S. Project.


The experiments show that the initial hypothesis was correct and pickled vegetables do indeed glow when a voltage is applied. It has been shown, that the effect is more pronounced in pickled onions which may be due to their smaller size allowing a larger current to flow. Pickled gherkins have a less intense glow but generate a lot more smoke than their spherical counterparts.

The electrode at which the reaction occurs appears to be arbitrary, but once it is going it is self perpetuating in that it continues to happen at that electrode.

Further Research

A lot more research needs to be done in this oft overlooked area of science, in particular investigation into non-pickled vegetables and fruit as well as other pickled foodstuffs such as walnuts, red cabbage, etc.

In relation to the experiments carried out here, analysis of the particles in the smoke from the electrified subjects and maybe more detailed investigation into how the amount of current flowing is related to the luminescence of the subject would have been helpful but were unfortunately outside the range of available equipment.

Further Reading

We have since discovered pioneering work has already been done in this field by the fine people at Digital. Their comprehensive writeup is well worth reading (if you can find it now that Compaq have bought DEC) despite its lack of pictures.

These page were inspired by the work of many dedicated scientists around the world.

The Team

The team consisted of Ben Waine, John Penton, John Hall, Chris Reed and Ross Younger pictured from left to right below.

Group Photo Group Photo

Page written by John Hall, John Penton, Ross Younger and Ben Waine. Last updated 12:55 14/3/98.

With thanks to Dr. Peter Robinson for the loan of an Apple Quicktake Camera.