I waited a long time before posting this because I wanted to make sure these will work…but others have verified this with certainty on the MyLesPaul forums, so here it goes.
I posted this a while back as “The Secret Weapon” – which was, of course, a hand-made capacitor. A capacitor (for those who don’t know how this works) is essentially created when a dielectric is sandwiched between two metal plates, such that the plates aren’t touching. In an oil and paper capacitor (like the vintage ones by sprague etc.), the dielectric is paper that has been soaked in oil. The oil is then sealed inside the casing of the capacitor.
Guitar capacitors are obviously not flat like two metal plates – these caps are made using the same principle, but rolled up (hence the cylinder shape). This created quite a stir on the MyLesPaul forum so I’m posting it here so others will also be able to give this a shot.
First step is to cut out four pieces of material. First you need two pieces of foil of equal size (though one will be shortened later on).
You also need the dielectric – I used paper. You need to use a very thin paper – you can order onionskin paper online or use something like dictionary or bible paper (also available online – don’t be cutting up a bible or a dictionary to make capacitors!).
You’ll want to solder two wires onto the two foils. You can strip the fiber off of some regular push back wire and use that since we’ve all got lots of that stuff lying around. Make sure that you solder the wires on opposite sides (not both the same) so that when you roll it up the wires come out of each end of the roll.
Next step is to sandwich the paper between the two sheets of foil. It is SUPER important that the two plates do not touch, otherwise you will short the cap and it will be garbage. As a result, the paper is cut just a little bit wider and longer than the foil. You can see here I’ve used a small piece of double stick tape to hold the layers in line (don’t use much, and put it at the end that will be rolled first, not the other end, as I’ve done here).
When finished you’ll want to add one more layer of larger cut paper on the bottom. You want the pile in this order: Paper -> foil -> paper -> foil.
The paper on the bottom layer will become the outside of the roll. When that’s done, roll it up – make sure everything is lined up perfectly and the foils are not touching. Roll it as tightly as you can.
As a side note, I took the picture below before cutting the inner foil piece. It’s a good idea to shorten the piece of foil on the inside of the roll by 5 mm or so so that it doesn’t go past the edge of the paper when everything moved as its being rolled up. I did this here but it’s not pictured.
Tape the roll once its rolled up so it doesn’t come undone.
The next step is to make a casing. You can use what you want for a casing, but I’ve found this method actually works quite well. Start by wrapping the roll in masking tape, cut slightly larger than the length of the roll itself (you’ll need one of those larger roles of masking tape, not a regular one).
Fold down the edges of the tape (since it was longer than the roll) to close one end (leave the other end open for now). Then seal it shut with CA glue.
Then, you’ll want to rub the rest of the outside of the casing with CA glue to seal it. The idea is that this outer casing should be water tight – if it isn’t, the oil used to fill the cap will leak out all over the place.
Once it has dried, flip it over and fill the casing with oil from the other end. You can use mineral oil, or most other oils. Freddy G used WD-40 I believe, and his worked very nicely. I don’t think the type of oil used should make an incredible difference in capacitance.
Once filled, close up the other end of the cap and seal it with CA glue as well.
Next up, it’s time to wrap the whole thing with a piece of paper that has been backed with double stick tape. This should extend just slightly longer than the length of the casing. The reason is that this will hold the epoxy used to conceal the casing.
Mix up some 5 minute epoxy, and dye it black.
Use this mixture to fill the ends. You can do one at a time, or do both – but if you do both, be aware that you will need to hold it and rotate it so that the epoxy doesn’t drip out of the sides (its easier to do one side at a time, which means mixing two smaller batches of epoxy instead of one).
Finally, it’s time for the label to go on. I design the labels in photoshop, then print them off and relic the paper so it has a nice look to it. The label is backed with double sided carpet tape.
And here is the finished product, with the label applied.
Looks pretty awesome if I do say so myself!