Not too long ago, a friend of mine showed me a sheet of wood in which there were lightning-like branches burned into it. He told me that someone had used a high-voltage power supply along with some electrolyte solution to wet the wood. The method is called "Lichtenberg wood burning" and can actually be done on more than just wood. The Wikipedia entry (https://en.wikipedia.org/wiki/Lichtenberg_figure) describes how it can be done in acrylic or even human skin (if they've been struck by lightning--not something I hope anyone would make an Instructable about!). Naturally, I wanted to try this wood burning technique myself!
There are many how-tos already out there to make the power supply and apply the technique, so my "spin" on it is to make a Lichtenberg figure Fidget Spinner!
This project combines two parts: the making the power supply from a microwave oven transformer and the making of the fidget spinner.
Step 1: Parts and Tools List
Admittedly, I did parts of this that were far more complicated than they need to be, specifically for the making the parts for the fidget spinner. You can feel free to save yourself some unneeded effort and make that part however you want.
For the power supply:
Microwave oven (NOT the one you currently use! It will not work again after you do this so unless you intend on buying a replacement, use a junked microwave)
Variable AC transformer (Variac or may be called a variable autotransformer)
Insulated, large gauge wire
Insulated ~12 inch rods (I used sections of 3/4" PVC pipe)
Electrical tape and wire nuts
For the Fidget Spinner:
1/4" ply wood
A few scraps of lumber for making clamping jigs
1/4" wood dowel (or whatever sized wood dowel you may have to plug a whole)
6 pennies (used as weights on the arms of the spinner)
Water and baking soda
608 ball bearing
Screw drivers (as needed to take apart your microwave oven)
Step 2: Fashioning a Power Supply
I happen to have a few discarded microwave ovens in my basement since my wife
enourages approves accepts tolerates doesn't know completely about how much junk I accumulate. Therefore, my high-voltage supply of choice for this project is the transformer out of one of these microwave ovens. From my understanding, most people who know what they're doing will prefer to use a neon-sign transformer, as they are safer to use for the type of discharges/arcs that may occur with this method. However, I assume that if you're not planning on making a living out of doing Lichtenberg Figures, you'll be fine for now. I suspect that the thin gauge wire used for the secondary winding of the microwave transformer may be more prone to short out when pushed at too high of current (e.g. when arcing).
This project also includes driving it with a variac (VARIable AC) so I can throttle back the voltage as needed when conducting the burning.
CAUTION: Working with high voltage is highly dangerous! You should only proceed if you comfortable about such activities and can take proper safety precautions. You operate at your own risk!
CAUTION #2: Inside the microwave oven is something called a magnetron. Some of these may contain a ceramic insulator for the tip made out of beryllium oxide (beryllia). While solid, it is harmless, but if you break or scrape off dust from it, it is highly dangerous to inhale.
After making sure the microwave oven is no longer needed to heat your Hot Pockets and popcorn, start ripping the thing apart. You should also have it unplugged of course! Each oven will be somewhat different, so you'll have to go about this using your finely-tuned senses on how to destroy things. I suspect most of the sheet metal screws are located either on the back or bottom. Most ovens I've seen have a fairly large sheet metal shell that encompass 3 of the sides. Removing this will reveal most of the innards. You need to locate the transformer which will likely be behind where the control panel was located. You'll also see a canister capacitor in the proximity of the transformer. You won't need the capacitor, but if you see it, you'll know you're in the right place. It's unlikely that the capacitor still has a charge, but it is wise to go ahead and try to short out the leads with an insulated screwdriver.
In my oven, I had to remove several screws and metal tabs to convince the frame to release the transformer from its evil clutches. For simplicity for later, snap a few pictures of the wiring before disconnecting anything. If it makes things easier for you, you should be able to remove the connectors leading to the transformer primary and secondary taps. There will likely be two wires that are connected to a few windings next to the secondary. From my understanding, these are for heating up the electron filament of the magnetron for thermionic emission. These two wires can be either disconnected or cut. Be sure to cap them off somehow. They will be a lower voltage, but higher current than the mains. There may be only one high-voltage line coming from the secondary. You will recognize the secondary because it will have a lot more windings with smaller diameter wire. The other wire for the secondary output may be simply a grounding to the ferrite core. You can probably reuse the same connections for the plug to the outlet.
After you have the transformer pulled out, you can set it in a convenient location or enclosure. I was lazy, so just left it on a leftover board. If using an enclosure, be sure to allow for ventilation. You may even need a fan to help push air around it to cool.
As I mentioned before, I plugged in the transformer to a variac so I can lower the voltage from the maximum. Some variacs may allow for over 100% from the wall voltage. I'd recommend not doing so since that is not what the transformer was designed for. But then again, I'm sure it wasn't designed for zapping wood fidget spinners either.
Lichtenberg figure burning requires you to be able to touch the surface of the wood with the two high voltage leads. Many people will use alligator-type clamps to fasten the leads to the wood. I have opted for probes that can be touched down and moved as needed. I extended the length of the high voltage secondary wire with some thick (12 gauge I believe), insulated, solid copper wire. I also attached a length of the wire to the bottom of the core to complete the two high voltage leads. I used electrical tape to secure the exposed ends of the wire to the ends of some 3/4" PVC pipe. The pipe I kept to around 12" long. A word of caution about using the PVC: if the PVC gets too hot, it can outgas and not be good or pleasant for your lungs. If done correctly, the pipe should not get too hot, but may be exposed to flame and smoke. Try to either extend the ends of the wire farther out to keep the PVC away from the business end or mitigate your burns from getting out of hand. The wood may catch fire, so keep this in mind.
I'll explain a little more about how to use this setup after we go over how to make the spinner.
Step 3: Make the Fidget Spinner
This part is what I consider overly complicated. I have a tendency to do that...
I originally wanted to make two halves of the spinner so I could embed pennies in the legs for the extra weight. I wanted the legs to be as uniform and reproducible as possible, so I didn't feel like cutting these out on a scroll or band saw. Looking back, I think it would have been just fine to use either of those! Instead, I decided to fashion a couple jigs to hold on to strips of plywood so I could use my miter saw.
First, I made a strip of the plywood on the table saw to give me a 1-1/2" thick of 4' long 1/4" plywood. I used a scrap piece of wood to chisel out a pocket for the wood to snugly fit into. The pocket should be the same width as the strip and also square in this case. You should chisel just deep enough for the wood to sit a little proud of the pocket. This way, you can use another piece of wood to screw down and clamp the strip.
With the jig made, I clamped it in place in my powered miter saw. I apologize I didn't take any pictures of this process. However, it was largely a trial/error kind of method. The plan is to make 3, identical pentagons (not regular pentagons, more like "house-shaped") followed by an equilateral triangle of 1-1/2" sides and then 3 identical rectangles that are 1-1/2" by roughly 1". To make the pentagons, I first started with 3 rectangles from the strip that were 2" long. You can use the jig for this if you want, but isn't necessary (although it does help keep your fingers away from the saw). Next, you clamp one of these pieces into the jig (make sure it's tight into the pocket corner) and set the saw to 30 degrees. It's alright if the corner of your jig gets chopped off as well. You'll want to make this cut such that it goes at least half way across the edge. Take it out of the jig, flip it over, and make the same cut. Due to symmetry, the apex of the "house" will be exactly in the center. Do this again for the other two pieces so you get 3 identical pentagons. These finish up the first half of the spinner.
Now to the other half of the spinner. Since I wanted the two halves to have overlapping joints, I couldn't just make both sides using the pentagons. So, I opted to make a triangle that would fit in the middle and then each side would get a rectangle to finish it out. You'll probably be wondering, "Pete, why did you go to so much trouble instead of just making each half using a solid piece of wood cut out on the bandsaw?". I'd respond to this by saying "How do you know my name, weirdo? And again, I know this is overly complicated and I should have just made both sides out of a solid piece that I cut out with the scroll saw.".
The triangle is made in much the same way as the pentagons. You'll still use jig and the miter saw set to 30 degrees. This time, you can start with a 1-1/2" square. You'll clamp this into the jig and make your miter cut such that the angle meets the corner of the square. Then, you'll take it out, flip it, and do the same thing to the other side. If done correctly, you'll have an equilateral triangle with sides of 1-1/2" inches. If you don't, sit down and think about it for a minute, have yourself a coffee, and try again. If you still don't, do yourself a favor and just make each half out of a single piece of plywood like you should have done in the first place. The last 3 rectangles can be cut such that they fill out the rest of the legs. You'll want to use the jig so it can hold onto the wood instead of loosing a finger keeping your hands too close to the blade.
You'll see in the pictures that I cut 3/4" holes into the pieces of the legs. These are to hold pennies. You can use any other coins if you want, but just use the appropriate spade bit. I used the spade bit so I could drill partially down and keep the bottom of the hole square. However, this still requires the point of the bit to make a hole all the way through, so I clean that up afterward by drilling a clean 1/4" hole and plugging it with a 1/4" dowel that is glued in. I drilled the pilot hole for the spade bit in the center of the rectangular pieces of the legs and then transferring the position to the pentagons so the two halves meet nicely.
I made a little clamping jig out of another scrap piece of lumber so I could glue the pieces together and hold them tight. The jig was made by screwing a short piece in first to make an end and then dry fitting the spinner to figure out where the other two clamp ends should be attached. I left a little gap so I could create clamping force with shims. Make sure to place some wax paper or painters tape along and in the whole jig so you don't glue the spinner to it!
Apply enough glue to completely cover the mating surfaces (but don't overdo it). Remember to put your pennies in the holes. I made the holes deep enough to put one penny in each side, you'll just stack the two on top of each other as you assemble it all. After the pieces are in place, add clamping pressure to the sides by pushing shims into the side. You could probably get away with only doing this to one side. It's a good idea to also clamp a piece of wood to the top and hold it all down (again, keep some wax paper in between parts you don't want to join).
After it's dried, cut some small plugs from a wood dowel and glue them into the holes above the pennies. It's OK if the plugs are a little long since we'll just sand it down anyway. Let the glue dry and sand everything down to smooth. If using a 608 bearing, drill out the center with a pilot drill and then a 7/8" spade or forstner bit. This is slightly oversized for the bearing, but I'll show you how to take care of that later.
Step 4: Electrocuting Your Fidget Spinner
I'd suggest practicing doing the Lichtenberg Figures on a scrap piece of wood before attempting it on the spinner. To do this, mix up some water and baking soda (sodium bicarbonate). You'll want to use enough baking soda to saturate the water. Just keep dumping it in until you get some settling to the bottom. Some people will heat up the water so more baking soda can dissolve. I don't think it's necessary. The baking solution is used to soak the wood so there is a conducting medium for the electricity to flow. The baking soda is a salt that forms ions in water. The ions are the electrolyte that give the water conductivity. DO NOT USE REGULAR TABLE SALT! Table salt, NaCl, or sodium chloride is also an electrolyte when dissolved in water, but is hazardous in this case because the chlorine may get kicked out during the high-voltage burning. The chlorine gas is not good to breathe!
The wood should be relatively clean and ideally sanded somewhat to open the pores of the wood. This will allow the solution to wet and soak into it better. Use a brush, rag, or paper towel to get the top of the wood wet with the solution. Let it set for a little bit to allow the wood to soak it up. The surface should still be wet.
This is the hazardous part. You should make sure all flammable materials are far away. Also, wear appropriate safety gear such as gloves and safety glasses. There will be smoke generated, so it's advisable to use a dust mask or respirator with proper ventilation. Keep everything insulated and isolated so there isn't a risk of grounding the arc or a return path to you.
Connect the microwave oven transformer to the variac. Most variacs I've seen simply have an outlet to plug normal cords into. If your variac has an on off switch, turn it off and turn the variable output to zero. Plug the variac into an outlet. I used a power strip that includes a circuit breaker. You should not expect the breaker to do you much good in this situation to provide any safety since the secondary of the transformer is isolated from that circuit. You must rely on your judgement to keep yourself safe. At this point, there should be no power to the transformer.
Your leads should be in a safe and neutral location so they won't be arcing on anything yet. Turn on the variac and slowly adjust the variable output to about the 50% position. This will be enough to give you some time to practice. Later, you can crank it up to 100% when you have a feel for how the arcs travel in your wood. You can always back off on the output if you want. I found it convenient to lower the voltage when trying to get some smaller areas.
Touch the probes to the wood at the two farthest ends. At first, you may get some arcing/burning, but it might slow or stop as the water evaporates. This is normal. Simply turn off the supply, reapply some solution, and go again. You should start getting some good arcing and branching. Some wood may be harder to get to branch than others because of the grain. Usually, the main branches will follow the grain direction, so depending on the look you're going for, you may want to do more diagonal placements of your high-voltage leads.
The arcs will grow toward each other (perhaps somewhat meandering) as long as there's still voltage and solution available. Stop the progress before the two opposite branches meet. If allowed to continue the branches will join and cause a low-resistance path. Typically, I've seen this produce an intense arc. Likely, this will reduce the life of your transformer and maybe even yourself if the transformer fails catastrophically. I have yet to experience the transformer failing, but I understand there is the possibility, especially if I arc it. Those secondary windings are awfully thin. Most likely, you'll get some flames started on the piece. This is alright as it can help get some of the branches deeper. Just be careful as the flames can also help arcs to jump easier.
If you still want to fill in some space, but already have branches getting close to each other, turn the voltage down. This will give you a more fine control over the burning.
Now that you've got some practice, try it out on your fidget spinner. I suggest starting at a low voltage again since the spinner doesn't have a very large area. After you're satisfied with both sides, use a stiff-bristled brush to clean the branches of soot. Some people use running water or compressed air to assist with this. If you use water, you'll need to wait longer to finish up with lacquer. I sealed mine up with a couple coats of spray lacquer. Overall, this darkened the wood a bit.
Step 5: Insert the Bearing
Dry fit the bearing into the central hole. It should fit easily with a little wiggle room. If it's too tight, you can open it up with a small drum sander. Ultimately, the bearing needs to fit snug, but not too tight that you risk breaking the wood.
In order to shim up the bearing to fit tighter, I put one wrap of electrical tape around it, being careful not to get any tape on the balls or races. I taped it in such a way that one edge of the tape was flush with the edge of the bearing and the other side overhanged. I used this excess to help pull the bearing through the hole. After the bearing is completely in the hole, trim off the tape.
Step 6: Finger Pads
I used a 1-1/4" hole saw to cut out a couple discs of wood. I decided to add a little fender to the discs to keep them separated from the bearing and only touch the inner race. This could be done in a lathe. Even though I don't have one, it didn't stop me from using other tools in ways they weren't intended. So, I clamped one at a time on a machine screw with a few nuts to tighten down on it. This was chucked into my drill press. I clamped a coping saw upside down in my drill press vise. With the press spinning, I slowly brought it down on the eagerly awaiting saw blade and used it to "face" the disc and leave the little ledge. I used a file to smooth it out a little bit and better define the ledge.
I took the two discs and enlarged their holes with a 5/16" bit, which corresponds with the wood dowel that is just a little smaller than the inner diameter of the bearing. I pressed the dowel into the discs and dry-fit the bearing to make a sandwich of them. This let me know where to cut the dowel off. After marking the cutoff location and dismantling the spinner, I cut the dowel to size and glued it to one of the discs. If you're like me, you might shy away from commitment (don't tell my wife!), so the spinner works fine by leaving the other side as just press-fitted onto the dowel. Alternatively, you can countersink one side and add a screw through it. I've found that the screw may start stripping the hole and work itself loose over time, so I prefer the press fit. You can then remove the finger pads and clean out or replace the bearing.
The dowel for the finger pads will need a small amount of tape as well to make a tighter fit. I found that scotch tape is a little thinner and gave me more precision in adding thickness than the electrical tape. In the end, either will work fine. Press the pads together. The spinner is now functionally complete. I sanded down the dowel to make it flush with the pad.
I ended up adding a couple coats of spray lacquer to protect the spinner part. If you do this, you'll want to remove the bearing or tape it off to keep the lacquer from gumming up the bearing. Have fun fidgeting!