The art of burning wood with electricity produces fragmented designs, burnt into the surface of the wood. These designs are called “fractiles,” after the statistical principle of the same name. Without getting into complex descriptions of the mathematics behind the fractile, the basic idea is that each succeeding section is smaller than the previous. In this, it gives much the same appearance as a tree limb, breaking down into smaller and smaller branches. It creates quite beautiful designs, which are tree-like in their appearance.
The technical name for these branched designs is a Lichtenberg figure and the device used to make them is referred to as a Lichtenberg device. Lichtenberg figures can appear naturally, either due to industrial accidents involving high voltage or from lightning. Long-term breakdown of materials which have some dielectric or insulating capability will naturally result in Lechtenberg fractal images forming in the material, either on the surface or inside the structure. This can happen in solids, liquids or gasses.
Before discussing how to make these beautiful designs, I feel compelled to warn you that this can be quite dangerous. It takes a considerable amount of electrical current to burn the wood (over 2,000 volts at a high enough current to kill); enough to cause burns or even kill. For this reason, many woodworking organizations don’t allow the display of works that include Lichtenberg burning of the wood.
- It is more or less impossible to make it fully safe to use a Lichtenberg device to burn wood, without going to extremes in creating an insulated case with interlocks. However, a few basic safety measures will make the dangers associated with burning wood manageable:
- To start with, keep tight control over the electric current, ensuring that the device is unplugged when not needed and double checking that it is switched off before making any contact.
- Always wear rubber gloves and only make contact with the wood or the device with one hand at a time, with the other hand held behind your back, where it cannot make accidental contact. The electric current can still burn one hand, if it makes contact in two places, but the current will not pass through the heart, as it would if you accidentally made contact with both hands. Current traveling through the heart would be fatal.
- Be sure to have a second person with you, also wearing rubber gloves, whenever using a Lichtenberg device. This person’s sole purpose in being there is as a safety measure, to shut off power if you get electrocuted.
Please note that it is actually the amount or current (amps) that kills, not the amount of volts. Nevertheless, the Lichtenberg device will produce enough amps of power to kill.
The Lichtenberg Device
The actual device used to make these beautiful designs is rather simple, consisting of an AC transformer that will boost 120 volts AC house current up to a minimum of 2,000 volts. The two most common sources of these transformers are those used for neon signs and those scavenged out of microwave ovens. Of the two, a transformer from a microwave is less costly, although it requires more work. However, the higher voltage that the neon sign transformer produces will result in finer figuring in the wood.
Transformers for neon signs are also easier to use, as they essentially come prepared for use. The power cord will be attached to the transformer, with output leads attached to the other side. About all that will need to be done is to attach battery clips to the output leads.
Making a Lichtenberg device from a microwave oven is a bit more complex. First, the oven must be disassembled and the transformer removed. Take the power cord as well, as it can be reattached to the input side of the transformer, saving the cost of a cord. On the output side of the transformer, there is a single lead. That’s where one wire will need to be attached. The other (ground) lead will need to be attached to the case of the transformer. As with the neon sign transformer, attach battery clips to the output leads. The two long wires from the output side of the transformer will not be used. Cut those wires short and put a wire nut on them to insulate them, taping the wire nuts in place with electrical tape.
The type of battery clips I’m referring to are not the ones used on jumper cables, although they are of the same style. Look for something that’s a smaller version of those. Avoid alligator clips, as those aren’t heavy-duty enough. The clips will usually have colored plastic tubing (red and black) over the handle end. Slip the tubing off of one side of the handle and slide it over the wire. This will expose the contact portion of the clips, which is usually built into both sides. Strip off enough of the insulation from the end of the wire to fit all the way into the handle and slide the stripped wire into the contact area, crimping the ears over onto the wire to hold it in place. If a soldering iron is available, solder the wire to the clamp handle for maximum security and current flow.
Better quality battery clips will have a screw inserted into the handle, allowing the wires to be attached more firmly. In this case, loosen the screw and wrap the end of the wire clockwise around it. Then tighten the screw to grip the wire. There will still be ears for clamping the wire in place and preventing it from pulling out.
Please note that these two options are not the only options available, just the most common. A minimum of 2,000 volts AC is needed; however the more volts the better. High current is not required and in fact is what makes the process dangerous. So, if it is possible to find a high voltage, low current transformer, that’s ideal. A transformer from an old CRT color television, for example, will produce 25,000 volts, if one can be found.
Burning the Wood
Literally any wood can be used for Lichtenberg burning, from oak to MDF. However, the best results seem to come from fine-grained woods, especially when those woods are used as a veneer face coating on plywood. Birch plywood is pretty much ideal for this, although Luan words well too. Using plywood provides a thin veneer to burn, while the rosin adhesive used to glue the layers of the plywood together will stop the water from soaking further into the wood, keeping the burn at the surface. MDF on the other hand, will absorb water rapidly, allowing the burn to go deeper. But since MDF doesn’t have a grain, it allows the burn pattern more freedom to go where it will, rather than following the wood’s natural grain.
Wood alone is not a good conductor, so some sort of conductive solution needs to be used with it. Many people use salt water for this, which works, but a saturated solution baking soda, dissolved in water works better. The baking soda ionizes the water, allowing it to conduct electricity just enough for our purposes, although not as well as wire will. A ratio of one tablespoon of baking soda per cup of water is just about ideal. Make sure that all the baking soda dissolves and doesn’t just settle to the bottom. heating the water can help, as hot water will naturally allow more of a substance to dissolve in it.
It is necessary to work on a non-conductive surface; ideally a rubber mat. But if that is not available, then one of those plastic folding tables is just as good. Another option is a wide, shallow plastic bin, of the type which is used to store clothes under the bed. Place the wood to be burned on the insulator and wet it down with the baking soda and water solution, soaking the surface. A sponge, brush or spray bottle can be used to apply the solution.
Check that the Lichtenberg device is disconnected and then attach the two battery clamps to opposite ends of the wood, using one hand only. You want to connect them in such a way that the electricity can follow the grain in the wood, as it goes from one to the other. Then plug in the machine and turn on the electricity.
You should immediately begin to see the wood sparking and burning adjacent to the two clamp. It will continue in this manner, working its way to a meeting point, somewhere in the middle. Don’t be surprised if the burning starts at one end before the other or that one end seems to be burning faster than the other. A lot will depend on the grain in the wood and how well it soaked up the solution.
It is possible to steer the burning process somewhat by spraying more solution onto the wood in areas where it is not burning sufficiently. For example, if the burn is going off to one side of the board, leaving the rest alone, then adding more solution on the side of the board that is not burning will most likely cause an additional trail to start in that area. Other than spraying on more solutions, there really isn’t much that can be done to control the pattern being created. This is nature at work and all we can do is watch and in this case, pull the plug when we decide that it is done. When it is done, remove the clamp, again using only one rubber glove coated hand for safety.
Optional Contact Method
Another option for making contact with the wood is to pound nails into the wood in different parts of the board. Only use uncoated nails for this. This provides the opportunity to create a more directed pattern, as the battery clamps can be attached to any two of those nails, burning only the surface of the wood between them. Let’s say that the desired pattern look something like a horseshoe; then a series of 6 to 10 nails could be pounded into the wood, forming that shape. The battery clips could then be moved from one pair of nails to the next, burning the space between each pair. Once completed and the mails are removed, it will look like the desired horseshoe.
Another way of doing this is to put the nails through a couple of non-conductive rods, like dowel rods or plastic pipe. The nail points can then be set onto two different points on the wood and moved around, as desired, to control the burn pattern. With such a system, more of the surface can be burned.
Finishing the Burnt Wood
As the wood burns, there is a considerable amount of carbon formed on the surface, following but also obscuring the actual design. Once the wood has been burnt to our satisfaction and we pull the plug, we need to remove the excess carbon. That can be done by brushing the surface of the wood with a nylon brush, like a toothbrush, under running water. The water is needed to wash away the carbon as it is broken up by the brush, so that it doesn’t get pressed into the wood pores.
Please note that this is a natural burning process, even though the circumstances of it are totally artificial. As a natural process, we have little to no control over how it ends up looking. Sometimes the results are amazing, while others are not as interesting. It may be necessary to make more pieces than needed, so that the best can be selected for use.
The resulting pattern is going to look something like lightning burnt into the wood. Finishing is required, preferably with a urethane varnish, to protect the burnt pattern and keep the remaining charring from rubbing off. Use several coats, allowing them to soak in, until there is a good buildup of finish over the burnt part of the wood.