Agents of Shield…ing: A Guide to Guitar Shielding

Single coil pickups are the source of some of my favorite sounds on the planet. As a player who cut his teeth on humbucker-equipped instruments, I thought I had it all figured out until I stumbled upon my first good Telecaster. And when I found the Jazzmaster––rather, when it found me––I finally knew how to get that sound that I’ve had in my head since I started playing.

As good as they sound, the problem of 60 cycle hum has been and will always be persistent, though many of us who swear by single coil pickups have either simply gotten used to it. Some have even developed tricks to mitigating unwanted noise, like finding that magically noiseless spot on stage and staying put, using a volume pedal to kill your signal when you’re not playing, or adding a hum eliminator of some kind to your signal chain.

Those are all fine ideas, but in the war against noise, the best, first line of defense is shielding.

The Front Lines

Shielding the guitar entails lining the control and pickup cavities with a layer of electrically conductive material in order to reject as much outside RF (Radio Frequency) interference as possible. I say “as much… as possible” because shielding alone won’t kill 100% of the interference, but the difference between ‘with’ and ‘without’ it is staggering.

This is a must-have modification for all of my personal guitars and one that I recommend wholeheartedly to customers and friends alike.

Which Material?

I prefer to use foil tape over shielding paint for a few reasons, the main ones being that paint requires more than a few coats to work properly, as well as being much more difficult to test for continuity using conventional methods. After all, paint is paint; graphite particles suspended in paint have much greater resistance than one layer of foil. Plus, I just like working with foil; as Data might say, “I have become accustomed to its sensory input patterns.”

Copper tape is generally considered to be superior to aluminum, but I’ve had good results with both. While there’s no contest that copper is indeed the better conductor, I haven’t found it to be so much better that it’s worth the additional price. I plan on revisiting this in the future, but for the purposes of this blog we’ll be using aluminum.

Doing the Deed

Now, I’ve removed enough balled-up foil over the years to know that just because I find something easy to work with, that doesn’t make it so. The truth is, shielding a guitar yourself for the first time––even the first few times––isn’t an easy thing to do. Trying to cleanly line a cavity while simultaneously ensuring that all of your pieces have continuity with each other can be a maddening exercise. Here’s how I do the job cleanly and efficiently:

What You Need

-Foil tape

-A razor blade of some description

-A multimeter to test continuity

I prefer to use a roll of adhesive-backed foil for this job, easily obtained from the hardware store of your choosing. You can also order aluminum or copper tape from most guitar parts suppliers but they normally sell it in lesser quantities and at a premium. Be sure that the foil tape you use has conductive adhesive, as many brands use a non-conductive backing that makes this job much trickier and more labor-intensive. It’s incredibly frustrating to do a nice, clean job only to discover that none of it works.

And honestly, don’t bother with spray adhesive and plain foil. It’s messy and easy to ruin.

I use the same box cutter blades I always have, but any good blade will do the trick. An X-Acto knife would be an asset here, its long handle allowing for more fine control and a better view of what you’re cutting.

Tracing

I begin by unspooling an appropriate length of tape for the rout in question. I trace the shape of the rout onto the foil by firmly pressing my index finger along its edges. At this stage it’s crucial to remember that you’re tracing a two-dimensional version of a three-dimensional cavity. Take care to anticipate the way depths might change and how wires are routed through the body. Each rout will need its own tracing, and it’s important to know how they’ll all fit together.

Cutting

After I’ve traced the shape onto the tape, I use my razor blade to cut it out, making sure to press hard enough to cut through the backing paper. Once satisfied with the cutout, I’ll peel off the backing and line the bottom of the cavity with it. Because the top of a rout is generally the same shape as the bottom, it’s usually a good fit.

Lining the Cavity

When it comes to lining the sides of the cavity, I prefer to use a single piece of tape if I can help it; one continuous piece of foil is always more reliable than a few pieces spliced together. I crudely measure the length of the cavity walls, then cut slightly more foil from the roll than I need. Backing removed, it’s a simple job to line the sides of the rout. I’ll then trim down the excess material for a clean look.

Leave an Overhang

Be sure to leave a bit of an overhang, preferably in the vicinity of a screw hole. Doing so ensures contact between the foil on the body and the foil that we’ll be installing on the pickguard, something which many folks seem to forget.

Don’t Forget the Pickguard

Shielding works best when it’s comprehensive, so to really get the job done, you absolutely must line the pickguard as well. Shielding the guard is a much simpler, almost thoughtless enterprise, requiring only a few strips of foil to completely cover the cavities hidden by the scratch plate. I like to completely cover the surface of the guard and then cut out the control and pickup routs.

Checking continuity

Before you button up the guitar, it’s a good idea to double-check continuity between all of those bits of foil using a multimeter. Most have a function for conductivity, such as the unit shown here. When the probes are electrically connected to each other, the unit emits a beep, removing the guesswork and ensuring that you’ve adequately lined your guitar cavities.

Here I am, checking continuity on a single strip of foil for some reason

Troubleshooting 

If you find that two pieces of foil tape aren’t properly connected, or if you used foil with non-conductive adhesive, you can fix that by making a little bridge from one piece to the other. Cut a small strip of foil and mate it face-down to the back of a much wider piece of tape, then simply stick it across the seam between the non-conductive areas. Bam! Connection.

Once you’re satisfied with your work, reinstall the electronic components and screw the guard back into place. When you plug in again, you will be greeted with a much quieter instrument.

UPDATED: 9/27/17

Speak of the devil, check this out: loose foil stapled into the control cavity. That’s a new one for me. Don’t do this either.