What are Lichtenberg figures, and how do we make them?
(Last updated 05/17/13)

What are Lichtenberg figures?
How do we make our Captured Lightning® sculptures?
Video of a huge 15 x 20 x 2 inch sculpture being discharged
Lichtenberg figures are fractals
Other interesting properties: fluorescence, solarization, birefringence, and discharge-free zone
"Iced 'bergs" and negative Lichtenberg figures
Discharge current measurements... and a paradox
Natural Lichtenberg figures - fulgurites, natural tattoos, and fractal lightning,
Are there practical uses for Lichtenberg figures?
Captured Lightning Sculptures - fossilized lightning bolts
Can I make my own Lichtenberg Figures?
How can I get a Captured Lightning Sculpture of my very own?
References and Further reading
Other Questions? See our Captured Lightning FAQ

Doubly-Irradiated "Windblown Lightning" Sculpture This Captured Lightning® sculpture was created by injecting a polished block of acrylic with a beam of high speed electrons from a 5 million volt particle accelerator. Electrons were first injected from the left side, the specimen was rotated 180 degrees, and additional electrons were injected through the opposite side. This created two independent layers of electrical charge, each located about one-half inch below the surface. The internal charge layer on the right side was then manually discharged, creating a flash of miniature "lightning" within the charge layer above. Additional electrical discharges then grew between the right and left charge layers, forming a beautifully interconnected and complex 3D discharge structure. The entire discharge took place in less than 100 billionths of a second! The sculpture is illuminated from below by blue light emitting diodes (LED's). Each of our Captured Lightning sculptures contains an incredibly detailed, fractal discharge pattern. Unlike laser art, every one of our sculptures is truly unique. As they branch, the discharge channels become increasingly finer and hair-like, ultimately disappearing at the tips. The smallest discharges are thought to extend down to the molecular level. See our Frequently Asked Questions (FAQ) for a quick overview of how these beautiful objects are created. (Actual size: 3 x 3 x 2 inches)

What are Lichtenberg figures?

"Lichtenberg figures" are branching, tree-like or fern-like patterns that are created by high voltage discharges passing along the surface, or inside of, electrical insulating materials (dielectrics). The first Lichtenberg figures were actually 2-dimensional "dust figures" formed as dust in the air settled on the surface of electrically-charged plates of resin in the laboratory of their discoverer, German physicist  Georg Christoph Lichtenberg (1742-1799). Professor Lichtenberg made this observation in 1777, demonstrating the phenomenon to his physics students and peers. He reported his findings in his memoir (in Latin): De Nova Methodo Naturam Ac Motum Fluidi Electrici Investigandi (Göttinger Novi Commentarii, Göttingen, 1777). The translated title of Lichtenberg's paper is, "Concerning the New Method Of Investigating the Nature and Movement of Electric Fluid". The physical principles involved in forming Lichtenberg figures eventually evolved to become the modern-day science of plasma physics.

Professor Lichtenberg used high-voltage electrostatic devices to electrically charge the surfaces of various insulating materials such as resin, glass, or ebonite (hard rubber). He then sprinkled a mixture of finely powdered sulfur and minium (red lead/lead tetroxide) onto the surface. He discovered that powdered sulfur (being slightly negatively-charged through friction with its container) was attracted to the positively-charged regions. Frictionally-charged red lead powder was found to be attracted to negatively-charged regions. The colored powders made previously hidden regions of stranded surface charge, and their polarity, clearly visible. Charged regions on the insulator surface were deposited by small discharges of static electricity. It is now known that, once deposited, electrically charged regions often persist on the surface of electrical insulators since the charges are prevented from freely moving and dissipating. Lichtenberg also found that the shapes of positively and negatively charged figures were significantly different. Positive figures tended to be star-like with long, multiply-branched paths, while negative figures tend to be shorter, rounded, and fan or shell-shaped. By carefully pressing a piece of paper onto the dusted surface, Lichtenberg was able to transfer these images onto the paper, demonstrating what eventually became the modern processes of xerography and laser printing. Drawings of some positive and negative figures that Lichtenberg created are shown below.

Positive Lichtenberg figure	Negative Lichtenberg figure

A number of other physicists and experimenters investigated Lichtenberg's figures over the next two hundred years. Notable 19th and 20th century researchers included physicists Gaston Planté and Peter T. Riess (mid-1850's), French artist and scientist Etienne Leopold Trouvelot, Thomas Burton Kinraide (late 1800's), and professors Carl Edward Magnusson, Maximilien Toepler, P. O. Pedersen, and Arthur Von Hippel (1920's-30's). Modern researchers often used photographic film to directly capture the faint light emitted by the positive or negative high voltage discharges. An English industrialist and electricity researcher, Lord William G. Armstrong of Cragside, published two very beautiful full-color books (now quite scarce!) showing some of the results of his high voltage and Lichtenberg Figure research. Fortunately, a copy of his first book, "Electric Movement in Air and Water, with Theoretical Inferences", was recently made available through the kind efforts of Jeff Behary at the Turn of the Century Electrotherapy Museum. In the mid-1920's, Von Hippel discovered that Lichtenberg figures were actually created through complex interactions between ionized gas (corona discharges and small electrical sparks called streamers) and the underlying dielectric surface. The discharges deposited matching patterns of electrical charge onto the dielectric surface below, where they became temporarily stranded. Von Hippel also discovered that increasing the applied voltage, or reducing the surrounding gas pressure, caused the length of the figures to increase.

The relationship between the length of Lichtenberg figures versus voltage was utilized to create early high voltage recording instruments, such as the klydonograph. Riess discovered that the diameter of a positive figure was about 2.8 times the diameter of an equal-voltage negative figure. These properties were later used to measure the peak voltage and polarity of lightning strikes. Klydonographs photographically recorded the size and shape of Lichtenberg figures that were created by abnormal electrical surges on electrical power lines created by nearby and direct lightning strikes. These allowed lightning researchers and power system designers in the 1930's and 1940's to measure lightning-induced voltages and polarities, thus providing critical information about the electrical characteristics of lightning strikes. This information was essential so that power engineers could create "man-made lightning" and then test the effectiveness of various lightning-protection approaches in high voltage laboratories. Lightning protection is now a critical part of the design for modern electrical transmission and distribution systems.  A schematic diagram of the main parts of a klydonograph is shown on the leftmost drawing below, along with examples of "klydonograms" from equal magnitude positive and negative high voltage transients. Notice how the positive Lichtenberg figure is much longer than the negative figure even though the peak voltage is of the same magnitude.

Schematic view of a klydonograph showing the position of the photographic film and high voltage electrode. Light from the high voltage discharges creates a photographic record of the event.	From W.W. Lewis, "The Protection of Transmission Systems Against Lightning", John Wiley & Sons, 1950

Lichtenberg figures are now known to occur during electrical breakdown processes within many gases, insulating liquids, and solid dielectrics. Lichtenberg figures may be created within billionths of a second (nanoseconds) when dielectrics are subjected to very high electrical stress, or they may develop over a period of many years through a progressive series of small, low-energy, partial discharges. Countless partial discharges on the surface or interior of solid dielectrics often create growing, partially-conductive 2D surface Lichtenberg figures and internal 3D "electrical trees". 2D electrical trees are often seen along the surfaces of contaminated power line insulators, and they can also form, hidden from view, inside dielectrics due to the presence of small internal defects or voids, or at points where an insulator has been physically damaged. Since these will eventually cause complete electrical failure of the insulator, preventing their initial formation and growth is critical to the long-term reliability of high-voltage equipment.

3D Lichtenberg figures were first created inside transparent plastic by physicists Arno Brasch and Fritz Lange in the late 1940's. By using their newly-invented electron accelerator, they injected huge numbers of free electrons into plastic specimens, causing electrical breakdown and the formation of carbonized internal Lichtenberg figures. Electrons are tiny, negatively charged particles that orbit the positively-charged nucleus of the atoms that make up all condensed matter. At their laboratory at AEG (Berlin, Germany), they used high voltage pulses from a multi-million volt Marx Generator to drive a pulsed electron beam accelerator. An article about their research and their accelerator (which they called a "Capacitron") originally appeared in the March 10, 1947 issue of LIFE Magazine. The Capacitron could deliver a three-million volt pulse, and could generate a powerful beam of free electrons with a peak current of up to 100,000 amperes! The glowing region of ionized air created by the exiting high-current beam of electrons resembled a bluish-violet rocket engine flame. A complete set of previously unpublished B&W pictures, including Lichtenberg figures inside a clear block of plastic, has recently become available online, as has another article with color pictures from the April, 1951 issue of Popular Mechanics.

The formal scientific study of trapped charges and their behavior within dielectrics was first conducted by the Brazilian physicist, Dr. Bernhard Gross, in the early 1950's. Dr. Gross confirmed that internal Lichtenberg figures could be created within a variety of polymers and glasses by injecting them with high-energy electrons using a linear accelerator (LINAC). The techniques that we use to make our sculptures are built upon the theoretical work and techniques originally developed by Gross, Brasch, and Lange. These 3D Lichtenberg figures are sometimes called electron trees, or beam trees. We call ours Captured Lightning® sculptures.

How do we make our Captured Lightning® sculptures?
Over many years, we have refined irradiation and fabrication techniques to create a wide variety of beautiful 2D and 3D sculptures. We start with carefully cut and polished shapes made from a clear, glassy polymer called polymethyl methacrylate (or PMMA). This material, commonly known as "acrylic", is sold under various trade names such as Lucite, Plexiglas, or Perspex. PMMA has a unique combination of high optical clarity and superior electrical and mechanical properties. Besides being an excellent electrical insulator, it's also clearer than glass! A number of other clear polymers, such as polycarbonate (PC), polystyrene (PS) , polyethylene terephthalate (PET), and polyvinyl chloride (PVC) can also be used to make Lichtenberg figures with varying degrees of success. However, most of these other materials tend to form dark gray or black discharge patterns instead of the sparkling, mirror-like figures seen within PMMA. Lichtenberg figures can also be created within glass. However, glass Lichtenberg figures may shatter upon discharge or (unpredictably!) some time later, so we no longer make them. 

We inject electrons into our specimens using a 150 kW particle accelerator called a Dynamitron. The heart of this device is the accelerator tube - a huge four-story high evacuated "vacuum tube" that operates at voltages between one and five million volts. At the top of the tube, electrons are emitted by a small, white-hot tungsten filament. The filament is also connected to the negative output terminal of a multimillion volt power supply, while the bottom of the tube is connected to ground and the positive terminal of the high voltage power supply. This configuration creates a very strong electrical field that accelerates electrons emitted from the filament to a very high velocity as they "fall" though the large potential difference towards ground. The bottom of the vacuum tube has very thin (only 2.3 thousandths of an inch thick!) titanium window that separates the high vacuum on the inside from air, at atmospheric pressure, on the outside. The high velocity electrons pass right through the titanium window, almost as though it wasn't even there! The electrons then emerge from the outside surface of the window, and then travel another 18 inches of air before crashing into our acrylic specimens on the movable carts below. Although the average lifetime of free electrons in air is only 11 billionths of a second, that's more than enough for them to work their magic inside the acrylic specimens below.

The energy of electrons leaving the accelerator is measured in millions of electron volts (or MeV). Most of our sculptures were created using electrons with energies between 2 - 5 MeV. At these energies, the electrons are traveling at relativistic velocities - between 98.5% and 99.6% of the speed of light. During irradiation, the speedy electrons are driven deep inside the acrylic before coming to a stop. The penetration depth is a function of the energy of the electron beam, the target material's dielectric properties, and its atomic density. The higher the energy of the electron beam, the deeper the electrons will penetrate. For example, electrons with an energy of five MeV will penetrate about one half of an inch into PMMA, but a sheet of lead only 1/16" thick will completely stop them.

When a thick specimen is irradiated, huge numbers of electrons accumulate inside, creating a strongly-charged cloud-like layer called a space charge. Because PMMA is an excellent electrical insulator, injected electrons become temporarily trapped deep inside. By passing specimens through the electron beam in two or more passes (changing specimen orientation between passes), or by rotating specimens while they're being irradiated, complex 3-dimensional regions of space charge can be created. Under continued irradiation, electrical charges accumulate and the electrical stress inside the acrylic dramatically increases. The electrical stress (E-field) and may reach many millions of volts per centimeter. We normally charge up our specimens just below the point where they'll self-discharge. Because the acrylic is an excellent insulator, the excess charges cannot escape, and the carts transport the fully-charged specimens out of the accelerator. We then force the specimens to discharge by poking them with heavily-insulated, pointed metal tools. The small divot creates a tiny region where the electrical stress overcomes the dielectric strength of the acrylic. The increased electrical stress breaks the chemical bonds that hold the acrylic molecules together, stripping away free electrons in a process called ionization. The newly-freed electrons are then accelerated by the extreme electric field, and these collide with, and ionize, more acrylic molecules. Portions of the acrylic abruptly become electrically conductive in a runaway process called avalanche breakdown.

Within billionths of a second, a network of branching, conductive channels form within the acrylic as, with a bright flash and a loud BANG, the material suddenly undergoes dielectric breakdown. The previously-trapped electrical charges rush out in a river-like torrent as thousands of smaller branches dump their share of charge into larger channels,  eventually merging into a single, brilliant discharge path that exits the acrylic. Although it appears like we're injecting high voltage into the block, we're actually removing the excess charges that were previously trapped inside. Dielectric breakdown occurs with incredible speed - the main electrical discharge within a 4 inch square specimen lasts less than 120 billionths of a second! Some solid state physicists now think that dielectric breakdown within a charge-injected solid is the most energetic (explosive) chemical reaction known, vastly exceeding that of high explosives. The following image shows a 12 x 12 x 1 inch specimen being discharged. In the image, a neutral density filter reduced the brilliance of the discharge so that the individual paths could be seen. Note the bright high-current discharge jumping along the top surface of the specimen to the grounded metal table below:

(Photo courtesy of Terry Blake)

As the miniature lightning bolts blast their way through the acrylic, they create millions of microscopic tubes and fractures, leaving behind a permanent "lightning fossil" deep inside the acrylic. The peak current within the electrical discharge reaches hundreds, or even thousands of amperes depending upon the size of the specimen. The hot plasma within the discharges causes the acrylic to melt and fracture along each path. Higher-current "roots" may lightly char the surrounding acrylic. The exit point of the discharge creates a small crater on the surface. Surprisingly, although we inject a huge amount of negative charge into our specimens, the electrical discharges originate from points which are more electrically positive (versus the space charge layer), so all of our Captured Lightning® sculptures are actually "positive" Lichtenberg figures!

Some specimens may "self-discharge" as they are being irradiated. This is usually caused by the presence of a small surface scratch, residual manufacturing stress, or a hidden internal defect. A self-discharged specimen will continue to discharge numerous times as irradiation continues. However, unlike the neat branched structures seen in manually-triggered sculptures, self-triggered sculptures develop a mat-like tangle of chaotic discharges or a complex combination of dendritic and chaotic patterns. Because of their complexity, self-discharged specimens are often among some of our most fascinating sculptures. 

Video of huge 15 x 20 x 2 inch sculpture being discharged:
Following is a short video clip showing a huge 15" x 20" x 2" specimen being discharged during our 2010 production run. This specimen was first charged on one surface by a 5 MeV electron beam. The fully-charged specimen was then (very carefully!) flipped over and irradiated once again on the other side. This created two independent charge planes, each located about 1/2" below the large surfaces. Prior to discharging, the estimated potential of these internal charge planes was about 2.6 million volts. Because of the two charge planes and large size, this specimen stored significantly more electrostatic energy than most of our other specimens - over four kilojoules! Safety precautions were necessary to prevent the possibility of receiving a dangerous electrical shock. Although the main discharge is very brief (under 500 billionths of a second!), the video successfully captured the brilliance of the 4 kilo-Joule main discharge in a single video frame (below). Numerous secondary discharges continued to flash after the main discharge. These continued sporadically for over 30 minutes. This video is courtesy of Bill Hathaway, GCL Laboratories. The resulting sculpture, cradled within a custom walnut light base and illuminated by an array of white and blue LED's, is also shown below.

(Click on above image for high-resolution image)

The rounded, crystalline flakes that make up the Lichtenberg Figure consist of chains of hollow tubes and tiny conchoidal (shell-shaped) fractures. Conchoidal fractures are characteristic of the way glassy (amorphous) materials fracture when stressed beyond their breaking point. The countless fractures behave as tiny mirrors, so illuminating a figure through an edge causes the entire Lichtenberg figure to glow brilliantly with the reflected colors of the external light source.

(Click for larger image) Figure 1. Dense Fern-like Discharges (maximum charge density). Fractal dimension ~1.8-1.9.

(Click for larger image) Figure 2. Dendritic Discharges (moderate charge density). Fractal Dimension ~1.5 - 1.8

(Click for larger image) Figure 3. Chaotic Discharges (prematurely discharged while being irradiated)

The self-similarity of dendritic discharges can easily be seen in the following sequence of zooms from a 12" x 12" Lichtenberg Figure. Although the branches become finer and hairlike, the overall branching structure remains similar until the finest tips ultimately disappear at the very edges of the discharge structure.

View Larger Map

Other interesting properties: fluorescence, solarization, birefringence, and discharge-free zone
When acrylic is irradiated by high-energy electrons, it glows brilliantly with a blue-white color. Radiation chemistry studies suggest that this is mainly due to luminescence that peaks at a wavelength of about 435 nm. However, acrylic also generates fainter glows from x-ray fluorescence, and Cherenkov radiation. The exact light-producing mechanisms for electron-irradiated PMMA are not fully understood.

Newly-irradiated specimens develop an amber-colored layer in the region between the surface(s) that were irradiated by the electron beam and the discharge layer. The phenomenon is called solarization, and it appears to be caused by a various interactions between high speed electrons and the acrylic's molecular structure. During irradiation, beam electrons are initially traveling at about 99% of the speed of light. As they penetrate the specimen, they collide with acrylic molecules, rapidly coming to a stop within a fraction of an inch. Electrons in the beam have a tremendous amount of kinetic energy, and as they suddenly brake to a stop, they release their kinetic energy in the form of heat and X-radiation. In acrylic, most solarization seems to occur in the regions directly hit by the beam of electrons. However, it has recently been found that regions that are intentionally covered by sheet lead (to prevent electrons from hitting some areas of the acrylic) may also exhibit solarization in deeper regions of the acrylic. As electrons crash into the lead mask, they radiate even more intense X-radiation that appears to create solarization even more deeply within the acrylic underneath the mask. Energetic collisions with electrons, x-rays, and excess electrons injected into the acrylic's molecular structure apparently stimulate chemical and physical reactions that alter the physical and optical properties of the acrylic. Deeply-trapped excess electrons may remain for years, creating color centers which also contribute to solarization. While some of these changes last for only minutes or hours, others persist for months or years. Some changes appear to be permanent. Although the specific causes of solarization are not completely understood, there is evidence that irradiation creates unstable, longer-lived "metastable" compounds that preferentially absorb light at the blue end of the spectrum (250 - 400 nm). Partial absorption of the blue portion of ambient light causes the solarized regions to appear green, brownish, or amber when illuminated by white light.

Most of our specimens turn a beautiful lime-green color immediately after irradiation. At room temperature and after discharging, this fades to amber over the next few hours. The amber region may then take months, or even years, to eventually fade away. Fading can usually be accelerated by gently heating the block in the presence of oxygen (or air), or by leaving the specimen in sunlight for an extended period of time. As oxygen diffuses into the acrylic from the outside surfaces and the porous discharge layer, it slowly bleaches the solarized region, causing the solarized layer to gradually become thinner and thinner, until it eventually disappears. Most older Lichtenberg figures are completely bleached. Although older specimens may no longer show any solarization, some may exhibit slight "fogging" due to radiation damage in the acrylic. Some specimens exhibit little initial solarization, while a small percentage of specimens permanently retain their amber color. Permanently colored specimens appear to be solarized via different, deeper penetrating mechanisms, such as X-radiation, since these specimens also tend to be uniformly solarized throughout the entire thickness instead of a relatively thin layer.

It has also been discovered that the solarization layer is often fluorescent. An amateur scientist from Australia, Daniel Rutter, discovered that monochromatic light from a green laser pointer changes color when passed through the solarized layer of a Lichtenberg figure. More recently, we have discovered that the light from a near-ultraviolet source (such as a Blu-ray laser or bright blue LED's) also causes the solarized region to fluoresce with a yellow-green color. Both effects appear to be due to one (or more) fluorescent components within the solarization layer. As the solarization fades over time, so does the fluorescence.

Most specimens also exhibit slight changes in the refractive index in the regions near the discharge layer. This is thought to be due to residual mechanical stresses near the discharge fractures. Residual stresses near the Lichtenberg figures can sometimes be seen as multicolored regions near the discharge plane when a sculpture is illuminated by polarized light and then viewed through a second polarizing filter (a configuration called crossed polarizers). When physically stressed, acrylic exhibits a property called birefringence. When viewed through crossed polarizers, stress-induced birefringence causes changes in color that are directly related to the amount and distribution of otherwise hidden stresses. An electrically charged specimen clearly shows internal compressive forces created by the high electrical field. These forces are then relieved when the specimen is discharged. Following are images of the same specimen prior to charging, fully charged, and then after discharging. Little internal stress is seen in the initially uncharged specimen. The specimen was then charged by injecting electrons from the left side. The injected charge forms an intensely negative layer of charge near the center of the specimen. At the same time, positive ions are strongly attracted to the external surfaces of the specimen. partially neutralizing the overall external charge outside the specimen. Attraction between the internal negative layer and the positively-charged outer surfaces create significant compressive stresses within the acrylic. These can easily be seen as colored regions on either side of the center in the middle image. After the specimen is discharged, the electrical stresses are greatly relieved as can be seen in the rightmost image. There are still residual mechanical stresses near the discharge zone due to fracturing. Click on any of the individual images to see full-size images.

Initially uncharged specimen	Fully charged specimen (electrons were injected from left side)	Discharged specimen

Finally, you'll notice that all of our sculptures have a discharge-free boundary along the outside edges. Because acrylic is not a perfect insulator, some of the internal charge can leak away along all the edges. The rate that excess charges can leak away is highest where the internal electrical field is greatest - i.e., in the region between the edge of the internal space charge region and the perimeter of each specimen. In these regions, the amount of stored charge is reduced to the point where it can no longer break down the acrylic. The result is a discharge-free zone along the perimeter of every specimen.

"Iced 'bergs" and negative Lichtenberg figures:
We have confirmed that fully-charged specimens retain their injected charge and their initial green color for several weeks when maintained at dry ice temperatures (-109F/-78.5C). One of our team members, Todd Johnson, has christened these "Iced 'bergs". At room temperature, the excess charge trapped within acrylic leaks away with an exponential time constant ranging from a few minutes to a few hours. Chilling specimens significantly reduces the speed that free charges can move within the acrylic, dramatically reducing the rate that trapped charges can leak away. At dry ice temperatures, trapped charges appear to remain stored indefinitely. Other researchers have stored chilled specimens for many months, and have discharged them with little, if any, difference from freshly charged specimens! This suggests that the initial green color may be related to the high density of electrons that remain trapped before discharging. Once discharged, even chilled specimens rapidly lose their green color, changing to the longer-term amber color.

We also discovered that chilled specimens develop a layer of frost when warmed in humid air. When we discharge a specimen, we produce a positive Lichtenberg figure inside the acrylic. Photographic evidence confirms that the exiting spark "wraps around" the exterior surfaces of the specimen, discharging the positive charges that were attached to the outer surfaces of the specimen. The external surface discharge produces a negative Lichtenberg figure along the large surfaces of the specimen. However, negative surface discharges are considerably fainter than the brilliant positive internal discharges, so they are normally very difficult to see or photograph. We accidentally discovered that, if the charged specimen is coated with frost, the discharges along the acrylic surface blast away the frost layer immediately above the discharges, making the paths taken by the negative discharges clearly visible. As can be seen in the image below, the resulting negative Lichtenberg figures left in the frost show considerably less branching than positive internal figures... just as professor Lichtenberg originally observed over 200 years ago. The following "iced 'berg" was discharged by Todd Johnson and Dr. Tim Koeth during our 2010 production run:

Discharge current measurements... and a paradox
During our 2007 and 2009 production runs, we measured and recorded discharge current waveforms for a number of 4" x 4" x 3/4" specimens. We designed a special holding fixture with copper foil plates that made physical contact with the large surfaces of a charged acrylic specimen. A heavily-insulated wire connected the pair of foil plates to a pointed discharge tool, and this wire was also passed through the center of a wideband Current Transformer (CT). When the specimen was discharged, the main current pulse flowed through the wire and was measured via the CT. The CT transformed the discharge current pulse that flowed through the wire into a voltage pulse that could then be captured and stored within a high speed Tektronix digital storage oscilloscope. The experimental configuration can be seen below:

One of the digitized waveforms is shown below. We found that, for this 4" x 4" specimen, the entire main discharge event occurred in less than 120 billionths of a second (120 ns), the peak current reached almost 600 amperes in 45 ns, and the waveform contained four discrete current peaks. Discharges from a number of other specimens showed between three and seven current peaks.

This suggests that propagating electrical trees may progress via a series of advancing breakdown waves. Each current peak may reflect a surge of newly conducting channels ("streamers" and "leaders") as they tap into new sources of stored charge. Newer channels apparently blast their way into previously untapped reservoirs of charge within the acrylic, pause briefly, then surge again, etc. The average discharge velocity was between 8.5 x 10⁵ and 1.3 x 10⁶ meters/second (526 and 790 miles/second, or around 0.3% the speed of light). However, pauses between successive current surges suggest that the peak discharge velocity during the propagation phases was even faster. Surprisingly, the average velocity within the specimen was actually 10-100 times faster than the velocity of positive lightning leaders in air. This is thought to be due to the extreme electrical field (estimated to be over 20 million volts/cm) at the tips of the propagating discharges within the acrylic.

The high streamer velocities within PMMA create a paradox, since they are over 800 times the speed of sound within PMMA. This is completely inconsistent with Griffith's theory of crack propagation within solids, which predicts that the maximum speed that cracks can propagate within a solid is limited to the speed of sound within the material, or about 1.6 x 10³ meters/second for PMMA. The current waveform clearly demonstrates that the breakdown process (the complete formation of chains of cracks and gas channels across the specimen) for our Lichtenberg figures propagates at speeds that are almost 1000 times FASTER than the maximum predicted by classical materials theory! A series of electro-optical measurements were recently made by Dr. Timothy Koeth in his laboratory at the University of Maryland. Dr. Koeth measured the time delay between optical (light) emissions at the beginning and ends of propagating discharges within 6" x 6" x 1" specimens. His measurements showed streamer velocities that ranged between 7.4 x 10⁵ and 1.55 x 10⁶ m/s.

Some insights into this paradox may come from a Russian researcher, Yu N. Vershinin. Dr. Vershinin explored how electrostatic energy is stored and released within solid dielectrics. Specifically, he studied how energy is stored within acrylic when charge is slowly injected (called "charge trapping") and the effects of rapidly releasing trapped charges ("charge detrapping") when the dielectric undergoes electrical breakdown. Vershinin proposed that, when a dielectric contains significant trapped space charge, the stored electrostatic potential energy is rapidly liberated, contributing to explosive formation and growth of crack tips. As chemical bonds in the surrounding material are ruptured, high pressure gases are liberated, expanding the channels behind the propagating crack tips. Vershinin speculated (and experimentally confirmed) that for very high internal electrical fields (E-fields), the potential energy initially stored within the E-field was rapidly converted into kinetic and thermal energy that drove crack propagation at hypersonic velocities. Vershinin found that this occurred only for propagating positive discharges within highly divergent E-fields. An American researcher, Dr. Paul Budenstein, has independently developed a theory of dielectric breakdown in solids that seems to explain many of the observations. Based upon the rate of channel expansion, Budenstein concludes that dielectric breakdown may be the most rapid chemical reaction in nature.

Evidence for the above theories of breakdown and discharge propagation can be seen within Captured Lightning Lichtenberg figures. Under high magnification, the discharge channels that make up the figures are found to be hollow tubes, surrounded by countless small fractures that scatter light. Some paths clearly exhibit periodic structures along the discharge channel, similar to beads along a string. These beaded structures are observed during dielectric breakdown of various polymers and crystalline ionic salts. The theories predict that under the extreme electrical field ruptures the chemical bonds within the acrylic. The resulting "electronic breakdown" (or electronic detonation) processes liberate gases as some of the insulating material is decomposed into its atomic constituents. Dr. Koeth has verified that a significant volume of gas exits from the discharge point when a specimen is discharged under water. Other researchers have determined that the evolved gases are composed primarily of hydrogen, carbon monoxide, carbon dioxide, and methane. "Beading" appears to be a repetitive sequence of electronic decomposition, evolution of gases under high pressure, and formation of new cracks ahead of the expanding gas zone. Following is an example of a beaded channel captured Bill Hathaway (GCL Laboratories).

Electronic detonation is hundreds of times faster than the detonation waves that propagate through even the fastest chemical explosives! Vershinin termed the explosive breakdown process "electronic detonation" since it was similar to the way that chemical reaction shock waves supersonically propagate through a high explosive as it detonates. Because of the large amount of electrostatic energy stored within our specimens, and the extremely short discharge intervals, the instantaneous power liberated during a discharge can exceed a gigawatt (10⁹ watts)! Not surprisingly, the discharge creates a loud BANG(!), and the brilliant, blue-white lightning-like spark channels wreak considerable havoc inside the acrylic as they blast countless permanent fractures and tubes along the space charge layers. Charge detrapping is now known to play a profound role in the degradation and breakdown of solid dielectrics that are subjected to long-term high voltage stresses, sudden voltage changes, or abrupt polarity reversals. In some respects, sudden charge detrapping in a solid dielectric is similar to a high-voltage capacitor discharge that occurs solely within the insulating material. 

After we discharge a specimen, hundreds of smaller secondary electrical discharges continue to flash throughout the specimen as small pockets of residual stranded charge continue to redistribute themselves. Large sculptures sparkle and sizzle, making a sound similar to frying bacon, and intermittent sparking has been seen over 30 minutes after the main discharge. These harmless secondary discharges often sting our fingers when we handle recently-discharged specimens. Click on the following image to see some high resolution video captured during one of our production runs that shows primary and secondary discharges.

(Photo and video courtesy of Mike Walker and Theodore Gray)
Click on the Above image to see a video clip
of many Lichtenberg figures being discharged

Occasionally, nature creates "fossilized lightning". Called fulgurites, these are hollow, glass-lined tubes that are formed when the powerful electrical current from a lightning strike creates underground discharge channels within poorly-conducting sandy or sandy-clay soils. The intensely hot channels from the lightning arc melt the surrounding sand and soil particles to form glassy tubes. Larger fulgurites often exhibit fractal characteristics as they split into smaller diameter root-like branches at further distances from the site of the main strike.



Lichtenberg figures, sometimes called "lightning flowers" or "skin feathering", sometimes form beneath the skin of unfortunate humans who have been struck by lightning. The victim often has one or more reddish radiating feathery patterns that branch outward from the entry and exit points of the strike. Here is an example of an electrical tattoo from a lucky lightning survivor:


OUCH! A temporary lightning tattoo on a "lucky" survivor
From "Lichtenberg Figures Due to a Lightning Strike" by Yves Domart, MD, and Emmanuel Garet, MD,
New England Journal of Medicine, Volume 343:1536, November 23, 2000
Medical terms for this phenomenon include arborescent lightning burn, arborescent (tree-like) erythema, keraunographic markings, or ferning patterns. Although the exact causes are subject to some debate, they appear to be the result of physical damage to capillaries under the skin, perhaps caused by the flow of electrical current, or by shock wave bruising from external flashovers just above the skin. These reddish marks fade away over a period of hours or days. They are recognized by forensic pathologists as clear evidence that a victim has been struck by lightning. The patient above survived with no permanent injuries, and the lightning flowers completely faded within a few days. A small Lichtenberg figure has also been observed at the entry point where a high voltage spark penetrated the skin of an unfortunate (but surviving) local electrical experimenter who was accidentally zapped by a homemade 60,000 volt Marx Generator. No... it wasn't me!

A similar phenomenon is sometimes seen when lightning hits a grassy field, as in this picture where lightning struck a golf course flagpole, leaving this beautiful 25 foot Lichtenberg figure on the green:

(From "Lightning and Lichtenberg Figures" by Cherington, Olson and Yarnell, Injury, Volume 34, Issue 5, May 2003)

Note the similarity between the figure above and the Lichtenberg figure below (illuminated from below by blue LED's):

High voltage discharges to the surface of water can also create Lichtenberg figures. Some beautiful examples of both positive and negative Lichtenberg figures on water surfaces can be seen on Dr. Colin Pounder's Lichtenberg figures web site. Natural lightning often creates transient "Lichtenberg figures" in the sky. Air is an excellent dielectric and, although the physical breakdown mechanisms for air and Plexiglas are considerably different, the appearance of the branching discharges is quite similar. So it should not be surprising that the branching forms of lightning leaders also have fractal characteristics. This similarity can clearly be observed during "anvil crawler" and horizontal "spider lightning". Spider lightning follows a thin, positively charged cloud layer, and the slowly propagating discharges can crawl across the sky for 30-50 miles - literally spanning from horizon to horizon. On a much smaller scale, transient Lichtenberg figures (sometimes mistakenly called St. Elmo's Fire) sometimes appear on the outer surface of cockpit windows of airplanes as they fly through thunderstorms.

Similar branching fractal patterns also occur when thunderstorms generate electrically conductive leaders that propagate downward from a charged cloud to the ground below. When one of these leaders connects with an unfortunate object on the ground, a high current pulse (called the return stroke) surges back upward through the completed path, resulting in a Cloud-to-Ground (CG) lightning strike. The peak current is typically tens of thousands of amps, and large positive bolts may reach several hundred thousand amps. Exceptional examples of downward propagating positive leaders have been captured by South Dakota lightning researcher, Tom Warner. Using high speed video imaging equipment, he was able to capture the downward progression of leaders and the return strokes from a positive lightning bolt. Positive lightning is a significantly rarer, and considerably more dangerous, form of lightning than negative lightning. Tom's "slow motion" videos show the air breaking down, forming glowing conductive plasma paths (called leaders) that fan downward from a huge reserve of charge within the cloud above. The brightly glowing tips of the positive leaders smoothly propagate, unlike negative leaders which propagate in a series of discrete jumps (called stepped leaders). The first descending leader to finally connect with the Earth below completes the circuit, resulting in a powerful Cloud-to-Ground (CG) lightning discharge. See Tom's web site to see his spectacular gallery of images and videos of positive and negative lightning.

Under special conditions lightning also creates transient upward-growing tree-like Lichtenberg figures. This phenomenon often occurs when broadcast antennas or mountain tops generate positive leaders that propagate upward into heavily-charged negative regions above. As the ground-based positive leaders propagate into the negatively-charged regions, they form a densely-branched positive Lichtenberg figure that, except for it's massive scale, looks quite similar to our Captured Lightning Lichtenberg figures. This fascinating phenomenon has been captured in another slow-motion video by Tom Warner - click on the following image to see the YouTube clip:

Lichtenberg figures can also be seen at some high energy pulsed power facilities, especially where deionized water is used as a dielectric to briefly store large amounts of electrical energy. The following photo is from Sandia National Laboratory's mighty Z Machine, the world's most powerful electrical pulse generator. After the completion of a high energy experiment, the water breaks down from the huge electrical stress, becoming an electrical conductor that safely dissipates unwanted residual energy from the system. The filamentary breakdown paths form Lichtenberg figures that dance across the water's surface. If you look closely, you'll notice that many of the paths actually trace out high voltage electrical field lines along the surface of the water. Although impressive, this display is only dissipating "left over" energy after the experiment is over. The discharges below represent only a very small fraction (perhaps 5%) of the initial energy that was used during the previous pulsed-power experiment.

(Click for a higher resolution 840 x 554 pixel image)

Are there any practical uses for Lichtenberg figures?
Analysis of the form and origination points of Lichtenberg figures is a powerful tool for diagnosing, and subsequently preventing, high voltage breakdown of solid dielectrics. By examining these figures, experts can diagnose and prevent future electrical faults within a variety of devices, such as high voltage transformers, capacitors, and insulators used by electrical utilities. Historically, Lichtenberg figures (created by HV measuring equipment such as Klydonographs) were a powerful tool for measuring the polarity and magnitude of transient overvoltages on power lines during direct and nearby lightning strikes. These early measurements were critical for the development of reliable electrical power transmission and distribution systems. Lichtenberg figures are still used as a forensic clue for identifying the cause of injury or death of human and animal lightning victims. Recent studies of Lichtenberg figures and charge detrapping in polymers are revealing important details on the mechanisms that are involved in the degradation and electrical breakdown of solid insulating materials.

There may be future medical applications as well. In 2009, a team of researchers at Texas A&M University proposed using 3D Lichtenberg figures created within various polymeric materials as "templates" for growing blood vessels (vascular tissue). There are significant similarities between branching Lichtenberg figures and animal circulatory systems - a fact not lost on many medical researchers. The hope is that, by creating branching 3D Lichtenberg figures inside a biodegradable polymer, such as polylactic acid (PLA), scientists can then use these as "molds" to support the development and growth of vascular tissue. Vascularization is essential for growing functional replacement tissues and organs. It's quite possible that the 18th century technology of Lichtenberg figures may ultimately play a critical role in organ growth and replacement therapy during the 21st century!


Captured Lightning Sculptures - fossilized lightning bolts
Captured Lightning® is indeed an accurate description for our sculptures. Holding a Captured Lightning sculpture is about the closest you can come to holding a fossilized lightning bolt. Each Lichtenberg figure is unique - a one-of-a kind treasure, sculpted in exquisite detail by the same titanic forces contained within natural lightning. Captured Lightning sculptures are completely safe - they have been completely discharged and they have no trace of radioactivity or X-rays.

Two dimensional photos cannot begin to capture the beauty and exquisite detail of our 3D sculptures. Following are a pair of 3-D images that can be rotated 360 degrees so that you can more fully appreciate the detail within some of our doubly-irradiated sculptures. Once the images have been completely downloaded, you can drag your mouse over the image to rotate each for a full 360 degree view. [Note: because of the large image size, a high speed Internet connection is recommended].

3D Rotatable Image	3D Rotatable Image
"Heavy Weather" (Courtesy of Theodore Gray)	"Windblown Lightning" (Courtesy of Theodore Gray)

Very few people have actually seen or held one of these rare objects of scientific art. Far fewer have had the opportunity to own sculptures as beautiful and spectacular as these. Stoneridge Engineering is proud to be the world's most experienced provider of these rare treasures.

Can I make my own Lichtenberg Figures?
Unfortunately, because electrons must be injected deep into the acrylic, it takes a multimillion-volt electron accelerator to make 3D Captured Lightning sculptures. However, 2D Lichtenberg figures can be made on the surfaces of some materials, such as carbonized Lichtenberg figures on wood, or as dust figures on the surfaces of some plastics. Some artists have used this technique to make 2D works of art. To make carbonized figures, a high voltage (HV) power source, such as an ignition coil or neon sign transformer, is required. The experiment should be done outside since it generates a significant amount of smoke and some small flames. Two nails or pins are pounded into the wood with a gap of 4 - 10 inches. The wood surface is then lightly sprayed with a saltwater solution to make it partially conductive, and the high voltage source is connected across the two nails. When high voltage is applied, carbonized paths begin to form near the nails. Accompanied by lots of smoke and even small flames, they begin branching as they grow towards each other. The heat from the process dries out the nearby surface, causing the branches to head in various directions, sometimes even in directions away from the opposite nail. The carbonized paths eventually grow to form Lichtenberg Figures with "roots" at each nail.  This technique must be done VERY carefully, since it involves using dangerously high voltages and water together. A method to adjust the voltage (such as a variable autotransformer or Variac) helps to control the discharge process and will improve the shape of the resulting figure. The following video clip shows this technique using a 9,000 volt 30 mA neon sign transformer as the high voltage source:



How can I get a Captured Lightning sculpture of my very own?
We offer a wide selection of Captured Lightning sculptures that range in size from affordable 2 x 2 inch specimens through museum quality two inch thick blocks as large as 15 inches by 20 inches. Please visit Gallery 1 or Gallery 2 to select a sculpture at the right price for you. We also offer a wide variety of lighted bases with white, blue, and multi-color color changing options. Many of these are available with UK, Australian, or EC power options. Our light bases illuminate the delicate patterns within, causing the discharge channels to glow so that the finest hair-like details become visible. We also offer a variety of attractively-priced factory 2nd sculptures discounted to 50% off regular price.  Be sure to visit our Eye Candy page to see some of the best artistic and experimental work by Stoneridge Engineering and some of our very creative friends.

Gallery 1	Gallery 2	Factory 2nds	"Eye Candy"

“A physical experiment which makes a bang is always worth more than a quiet one. Therefore a man cannot strongly enough ask of Heaven: if it wants to let him discover something, may it be something that makes a bang. It will resound into eternity.” – Lichtenberg, Georg Christoph, and Albert Leitzmann. 1906. "Georg Christoph Lichtenbergs Aphorismen: nach den Handschriften. Drittes Heft, 1775-1779," page 326. Originally in German, from Lichtenberg's Booklet F, Aphorism 1138, Oct 11-13, 1778.  (Thanks to Fermilab scientist and author, Bill Higgins for researching the source of the above quote). "Thunder is good; thunder is impressive. But it is the lightning that does the work." - Mark Twain

References and Further Reading:
1. Gross, Bernard, "Irradiation Effects in Plexiglas", Journal of Polymer Science, Volume 27, 1958, Issue 115, Pages 135 - 143
2. Hashishes. Yuzo, "Two Hundred Years of Lichtenberg Figures", Journal of Electrostatics, Volume 6, Issue 1 , February 1979, Pages 1-13
3. Chadwick, K. H., "The Effect of Light Exposure on the Optical Density of Irradiated Clear Polymethylmethacrylate", 1972 Phys. Med. Biol. 17, Pages 88-93
4. Chadwick, K. H., and Leenhouts, H. P., "Fading of radiation-induced optical density in polymethylmethacrylate on oxygen diffusion", Phys. Med. Biol. 15 No 4 (October, 1970), Pages 743-744
5. L. Niemeyer, L. Pietronero*, and H. J. Wiesmann, "Fractal Dimension of Dielectric Breakdown", Phys. Rev. Lett. 52, Pages 1033–1036 (1984)
6. Gardner, Donald G., et. al., "Radiation-induced changes in the index of refraction, density, and dielectric constant of poly(methyl methacrylate)", Journal of Applied Polymer Science, Volume 11, Issue 7, July 1967, Pages 1065-1078
7. Akishin, A.A.; Tseplyaev, L.I., "Edge effect in radiation-charge dielectric materials", Physics and Chemistry of Materials Treatment, v 31, n 1, Jan.-Feb. 1997, p 30-1. A similar paper is also contained within the book "Effects of Space Conditions on Materials", Akishin, A. I., Nova Science Publishers, 2001, ISBN 1590330285
8. Fothergill, J.C.; Dissado, L.A.; Sweeney, P.J.J., "A discharge-avalanche theory for the propagation of electrical trees. A physical basis for their voltage dependence", Dielectrics and Electrical Insulation, IEEE Transactions on, Volume 1, Issue 3 , June 1994, Pages 474 - 486
9. R. A. Galloway, T. F. Lisanti and M. R. Cleland, "A new 5 MeV –300 kW Dynamitron for radiation processing", Radiation Physics and Chemistry, Volume 71, Issues 1-2, September-October 2004, Pages 551-553
10. Sessler, G.M.. "Charge distribution and transport in polymers", IEEE Transactions on Dielectrics and Electrical Insulation, Volume 4 , Issue 5 , Oct. 1997, Pages 614 - 628
11. Karczmarczuk, Jerzy, "Dendrites in Nature and in Computer", Foton 84/SPECIAL ISSUE, Spring 2006
12. C. M. Foust, General Electric Review: Instruments for Lightning Measurements (Includes Klydonograph and Lichtenberg Figures), Volume 34, #4, April, 1931, Pages 235-246
13. Watson, Alan and Dow, Julian, "Emission Processes Accompanying Megavolt Electron Irradiation of Dielectrics", Journal of Applied Physics, December 1968, Volume 39, Issue 13, pages 5935-5940
14. Fujimori, S., "Fractal properties of breakdowns", Properties and Applications of Dielectric Materials, 1988. Proceedings, Second International Conference on Properties and Applications of, 12-16 Sept. 1988, Volume 2, Pages 519 - 522
15. Domart, Yves, M. D., Garet, Emmanuel, M.D., "Lichtenberg Figures Due to a Lightning Strike", New England Journal of Medicine, Volume 343:1536, November 23, 2000, Number 21, Images in Clinical Medicine
16. H. Hiraoka, "Radiation Chemistry of Poly(methacrylates)", Radiation Chemistry, March 1977, pages 121-130
17. Brown, R. G., "Time and Temperature Dependence of Irradiation Effects in Solid Dielectrics", Journal of Applied Physics, September 1967, Volume 38, Issue 10, pages 3904-3907
18. Yu. S. Deev, M. S. Kruglyi, V. K. Lyapidevskii and V. I. Serenkov, "Mechanism underlying the formation of dendritic or tree-like channels in a dielectric irradiated with charged particles", Atomic Energy, Volume 29, Number 4, October, 1970, pages 1037-1040
19. Ebert, Ute and Arrayas, Manuel, "Pattern Formation in Electric Discharges", p. 270 - 282 in: Coherent Structures in Complex Systems, eds.: D. Reguera et al., Lecture Notes in Physics 567 (Springer, Berlin 2001)
20. Yu.N. Vershinin, S.V. Barakhvostov, "Electron Processes in the Pulse Breakdown of Solid Dielectrics", 3rd International Conference on “Technical and Physical Problems in Power Engineering”, (TPE-2006), May 29-31, 2006 - Gazi University, Ankara, Turkey (covers detonation theory of high field breakdown in solid dielectrics)
21. Vershinin, Yu. N., "Parameters of Electronic Detonation in Solid Dielectrics", Technical Physics, Vol. 47, No. 12, 2002, pages 1524–1528. Translated from Zhurnal TekhnicheskoÏ Fiziki, Vol. 72, No. 12, 2002, pp. 39–43, ISSN: 10637842
22. Budenstein, P.P., "Dielectric Breakdown in Solids", Technical Report RG-75-25, US Army Missile Command, December 20, 1974, DTIC accession #ADA012177
23. C. M. Cooke, E. R. Williams and K. A. Wright, "Space Charge Stimulated Growth of Electrical Trees", Proc. Intl Conf on Properties and Applications of Dielectric Materials, Xian, China, 1985, Pages 1-6
24. N, I, Kuskova, "Spark Discharges in Condensed Media", Technical Physics, Volume 46, Number 2, 2001, pages 182-185
25. Theodore Gray, "Theo Gray's Mad Science: Experiments You Can Do At Home - But Probably Shouldn't", Black Dog & Leventhal Publishers, 2009, ISBN 978-1579127916
26. Jen-Huang Huang, Jeongyun Kim, et al, "Rapid Fabrication of Bio-inspired 3D Microfluidic Vascular Networks", Journal of Advanced Materials, Volume 21,Issue 35, pages 1-5, DOI: 10.1002/adma.200900584
27. Bejan, Adrian and Zane, J. Peder, "Design in Nature: How the Constructal Law Governs Evolution in Biology, Physics, Technology, and Social Organization", Doubleday, 2012, ISBN-13: 978-0385534611

Got other questions? See our Captured Lightning FAQ
One-page summary explanation (377 kB PDF file)
One-page summary in German (translated by Harry Meier - Thanks, Harry!)
Where can I get my very own Captured Lightning sculpture?