The fractal-like patterns in this platter are technically called Lichtenberg figure, and are the same sort of pattern that lightning makes in the sky. It’s fun to watch, and fun to do (if you have a bit of mad-scientist in you), although it is very dangerous.

How it Works (kinda)

Wood does not conduct electricity at all well, so just shocking wood doesn’t do the job. So I add a conductive solution (something wet) on the wood to carry the electricity.

The way I picture this working is that the solution conducts the electricity through the surface of the wood. The current heats things up, which starts to evaporate the fluid. Once the wood is just dry enough (in a tiny area), the electricity will jump a little arc and burn the wood there.

That burned spot now is mostly carbon, which conducts electricity reasonably well. So things move on to the next tiny spot. Those spots keep progressing into tracks. As this is a dynamic process, with things changing all the time (carbon tracks, water evaporating, etc) the electricity finds its “good paths” are always changing, which makes it branch out here and there. As that happens over and over, always changing, it makes the lightning or tree patterns.

If the solution doesn’t conduct well enough, nothing happens. If it conducts too well, the current is too strong and will find places to jump and arc which just burns unpleasant patterns. The arcing can also happen if a section of the wood dries out and the current decides to jump that gap.

The process doesn’t happen “lightning-fast”. It can sometimes take several minutes of electricity flowing to start the process (but sometimes it starts up right away). And it can sometimes take a minute or so to get one of the traces like in the platter above.

Safety

Electricity is dangerous. Seriously dangerous.

Most woodworkers know that a tablesaws and chainsaws are dangerous. Even if you don’t understand kickback or why a riving knife is a good thing, you can at least see some of the danger – a disk or chain containing dozens of sharp pointy bits, moving at very high speed.

Electricity is invisible. The danger is unseen. And most “normal” people don’t understand how electricity works at all. Flip the switch and the light comes on.

High-voltage electricity understood by even fewer people. Even those who work with electricity or electronics daily don’t generally understand the weird things that can happen at extreme voltages.

The danger is there but invisible. So it’s sort of like using a chainsaw in total darkness.

Electricity can kill you. Just a small current traveling through your body can shut down your heart. If you are lucky enough survive that, the current can burn you (internally and externally) and cause permanent cell damage to what doesn’t get burned. This is serious stuff.

One person I know ended up spending 6 weeks in the hospital enduring multiple surgeries, some amputations, and skin grafts. That doesn’t count physical therapy. She is lucky to be alive.

If you are going to attempt a project involving high-voltage electricity you need to take serious precautions. Precautions include:

• You should be able to easily and quickly tell when the power is on or off (an indicator light, etc)
• Always assume the power is on and act accordingly (assume your indicator light is broken)
• Have an easy way to turn things off (like a dead-man switch)
• Wear good rubber-soled shoes
• Keep one hand in a pocket (thus reducing the chance of electricity flowing between your arms and thru your heart)
• Switch off, and unplug often
• Always work as if the power is on
• Keep your work area clear and clean
• Keep the excess water dried up and keep the wires out of any puddles
• Never work alone
• You and your work partner must know how to contact emergency services

If you do all that, I still can’t recommend that you try this. If you need more encouragement, check out what wikipedia has to say about electrocution or electric shock or electrical burns.

Microwave Oven Transformers

On the internet, I see a lot of people using (or attempting to use) the transformer from a microwave oven to do this.

I strongly recommend against using microwave oven transformers.

A microwave oven runs at around 1KW – that’s a lot of power. The secondary (high voltage side) of the transformer is around 2000 volts.  It has no current-limiting ability built in – its intended use doesn’t require it.  So it will pump out just as much current as it can, until it burns itself up or trips the circuit breaker.

This has two problems: First, it is way too aggressive for burning wood. Too much current burns too fast and makes chunky fat traces without a lot of detail. That is my opinion.

Second, it is extremely dangerous. If you become part of the curent path, the transformer will pump high current through your body. If you do the math, you will find that the current on the 2000 volt could exceed 1 amp before it blows the circuit breaker in your house. This is about 30 times what is required to cause heart fibrillation, and more than enough current to cause permanent damage (from both burns and cell damage). It can also freeze your muscles so you can’t let go or move to help yourself.

The person I know who was horribly injured by a microwave transformer said she just basically waited there, holding the wires, unable to move until the circuit breaker finally blew.  Terrifying.

A neon sign transformer usually produces higher voltages, but they output much lower currents – usually 30mA to 60mA. Additionally, they are current-limited by design.

The lower current, in my opinion, allows it to burn better patterns in wood.  They are finer, with more detail, and less burning.  A 30mA transformer is plenty to do the job.

However, it is still not “safe” by any means: 30mA is enough to trigger heart fibrillation, which is usually fatal without prompt help. It is probably not enough to cause severe burns or cell damage. However, electricity and the human body are pretty complex things, and there are no guarantees.