Great foil for pickguards, etc., but not much else

[Usable Thought]

it is my understanding that Al does not block RF – only hum-buzz from faulty (unshielded?) rheostats. It may help around florescent lights (qualifies as EMI?), but I think it would have to be pretty thick to be significant. A ~1/16” thick Al pie tin will reduce SC hum just a bit when placed underneath. Even a reduction of a few dB can seem significant if the noise drops below annoyance level. I thought Cu was required for RF protection, though.

Curious where you heard this? My impression based on reading & personal experience is the opposite - that aluminum is just as effective. E.g. from Newark.com, who we'd expect to have reliable info, this PDF white paper makes no distinction between aluminum and copper shielding at all frequencies: Stop the Noise: The importance of being (properly) shielded.

The kind of metal does matter when dealing with magnetic flux, e.g. leakage from a leaky transformer - there you're not looking for a shield but rather something to persuade the flux to take the easy route close to home rather than head off to your sensitive circuitry. So special alloys with high EM permeablity, e.g. mu-metal, are used. But obviously that's different.

Back to guitar shielding -

Aluminum foil is something I use only when testing to see if shielding will help a particular guitar. Then, it's invaluable. It's easy to take a big hunk of foil and wrap it around the body to cover the controls - from the outside - and secure it temporarily to ground. Then see if it cuts the noise. For temporary connection, an alligator clip jumper from foil to grounded hardware is all that's needed.

For installed shielding on the other hand, I'd never use aluminum foil nor tape. The difficulty in achieving conductive overlap is enough to discourage. Fortunately copper foil tape or shielding paint work well (get the right brand of paint!), last a long time, and are easy to apply. My own preference is copper tape w/the conductive adhesive. Downside is $$$ but there are several brands to choose from & many retailers, so at least a little price competition; before I bought I did a spreadsheet to calculate max coverage per dollar. I don't know how long the adhesive remains conductive, but so far, +1 year on the single installation I did. I rely on the adhesive for overlap; for final connection to ground I prefer a mechanical connection though I suppose one could solder also. Possibly there is an expected-life spec for the adhesive; I've been too lazy to look for it but if I were doing the work for hire I would certainly check & if necessary call the company.

A long discussion about the merits pro or con of aluminum tape, or for that matter aluminum foil, doesn't seem that useful given the alternatives are so much better. Unless you are rock-bottom broke at the moment - which happens! - in which case, sure, figure out a mechanical connection that will last & go for it.

[rjb]

Curious where you heard this?

It sounds like someone who quoted someone who quoted someone who quoted Bill Lawrence.
Bill Lawrence Website

Now let�s talk about aluminum. While aluminum has some of the best acoustical properties it has, by far, the worst properties to use for the bridge plate. It�s like salt in a soup -- small quantities can perform miracles but too much will ruin your dinner. Aluminum has an extremely high eddy current potential and when placed under a pickup ( grounded or not grounded) can make a hum bucker hum like a single coil, or make a single coil as quiet as a hum bucker. This all depends on the thickness of the plate. At about �� thickness your single coil will be as quiet as a hum bucker, but you also lose about 60% output and about the same amount of highs. Leo used a .015 aluminum plate under the pick guard of his 54 Strat to reduce some of the hum and the buzz and take a little bit of the edge from the pickup, resulting in a very musical, sweet tone.

Aluminum has some strange properties, and it�s the only commercially available metal I know of that can eliminate the buzz caused by light dimmers. An inch thick copper or brass shield cannot reduce the buzz caused by light dimmers but .003 thick aluminum foil can! This is known some thirty years and the reason why Belden introduced double shielded cable ( Copper braid plus aluminum foil). There is one problem for guitar cords -- the double shielding makes the cable too stiff . It helps quite a bit when you shield your guitar with copper and aluminum foil.
Try this test-- wire a single coil to a jack and plug it into your amp. Put the pickup on a table next to your amp. Take an aluminum pan from your kitchen and put it slowly on top of your single coil and watch the hum disappear!

[big_teee]

Aluminum, copper, brass, can be used for shielding, and it needs to be grounded.
They have been used effectively in electric guitars for shielding for many years.
Different metals do react differently to magnetic fields, as previously stated.
Aluminum makes a fine shield, but as stated you have the problems of soldering, and conductivity between layers.
T

[rjb]

My impression based on reading & personal experience is the opposite - that aluminum is just as effective. E.g. from Newark.com, who we'd expect to have reliable info, this PDF white paper makes no distinction between aluminum and copper shielding at all frequencies: Stop the Noise: The importance of being (properly) shielded.
|
For installed shielding on the other hand, I'd never use aluminum foil nor tape. The difficulty in achieving conductive overlap is enough to discourage....
|
A long discussion about the merits pro or con of aluminum tape, or for that matter aluminum foil, doesn't seem that useful given the alternatives are so much better.

I think "better" is a subjective term here.

You've already noted that aluminum shielding is as effective as copper.

I might add that several major guitar manufacturers do shield their faceplates with aluminum foil.

Although shielding a cavity with a single piece of foil would be a pita, I know at least one manufacturer lines their cavities with what you might call a custom aluminum pie pan. As noted, there are easier ways to line a cavity.

IMHO, all control cases should be daisy-chained with bus wire to the output jack's sleeve terminal.

So, if you use a single sheet of aluminum foil on the faceplate, and one sheet of aluminum in the cavity (or line the cavity in some other manner), the only question is how to get continuity between the cavity shield and the faceplate shield. The answer is wire.

I've run a wire from a screw in the cavity (where the bridge ground wire was attached) to the output jack's sleeve terminal (which contacts the faceplate shield through mounting hardware). Of course, all aluminum contact points are cleaned and treated with anti-oxidation compound. An alternate configuration that doesn't tether the faceplate to the cavity was presented earlier in this thread, but seems to have disappeared.

[tedmich]

Al is a poor cousin to copper, which is king. I love the fact that my copper 1.4mil 3M tape at 0.25", 0.5" and 1 " wide is equivalent to
AWG
23
20
17
respectively

it solders beautifully and put it between two kapton layers and we have a wonderfully flat signal path right up against the ground plane.

Check this StewMac / Dan Erlewine shielding page
http://www.stewmac.com/How-To/Online...hielding_.html
near the bottom they show the internals of a Santana strat where every copper foil piece has been soldered together (!),

also a pic of the famous "super shielded" Danelectro with an internal brass box

[Usable Thought]

I think "better" is a subjective term here.

Well, yes - but for DIY'ers I'd still maintain that aluminum foil is a PIA (Does that work? DIY = PIA?). On the other hand, the guy who does the GuitarNuts.com site, and who I think is an excellent proponent of shielding, includes aluminum foil as an option in his procedure for shielding a Strat. So if he think's it's OK, I guess I should too.

As for mass market guitar makers, I would guess their way of operating is quite different. They have volume costs to consider; mentioning copper foil tape to them might draw a laugh. And likewise they can standardize even a quirky installation procedure. I would be curious to see what a custom guitar maker might choose for shielding.

EDIT: A good example of aluminum foil shielding comes from GuitarNuts - "Frank's Shielding Project." It's a flash slideshow with many pics such as this:

[rjb]

I'm a DIY'er, but do not consider anti-oxidation compound all that "sophisticated".
You can find it in the electrical department of the same hardware stores that sell aluminum tape.

[Usable Thought]

I'm a DIY'er, but do not consider anti-oxidation compound all that "sophisticated".
You can find it in the electrical department of the same hardware stores that sell aluminum tape.

Well, maybe I should just say I'm unsophisticated & leave it at that.

[big_teee]

The only place I use aluminum is glued to a pickguard.
Just Like Leo Did it! IMO it's good for that, and for that it's inexpensive.
T

[Leo_Gnardo]

Well, yes - but for DIY'ers I'd still maintain that aluminum foil is a PIA.

Aluminum a PIA for pros too. All I can see, it's a poor excuse for those who will not bother to source copper, and/or afraid of soldering. Only excuse left is if you live in a part of the world where copper foil, sticky or not, is just plain unavailable. When I see someone's bothered to make a video, and uses patches of electrical tape to stick bits of aluminum foil together, this has got to be a joke, right? "How to do a half ass job."

Copper IS the solution. Period.

"Until somethin' better comes along." Any excuse to quote Fats Waller.

[Steve A.]

Excuse me, I was just trying to help.
I'm gone!

Please come back!

[Steve A.]

I like to shield the backside of a strat pickguard to eliminate the scratchiness from static electricity. I prefer to shield control and pickup cavities with copper foil tape,* soldering all of the joints and sinking a screw with a black lead from the output jack ground lug in the middle to ground everything. I run narrow pieces of* copper tape over the side of the cavity under some of the screws securing the pickguard.

If there are tunnels between the cavities I solder a length of small gauge stranded wire from one cavity to the next.

Doing all of this will usually reduce the noise in a strat- but only the noise still present when using a RWRP middle pickup for the #2 & #4 position. Or more simply,* only the noise still present when using humbucking stacks or rails in your strat. Humcancelling does one thing, shielding does another.

BTW I doubt if anyone could actually hear the difference between a guitar shielded with copper foil vs aluminum foil assuming that they were both grounded similarly.

I suggested aluminum foil for strat pickguards because it comes in bigger sheets than copper foil. That is all I use it for besides cooking- its copper foil for everthing else. That picture from Dan E. looks like one of my strats- only I flow 60/40 solder over the entire shebang to shield against not just noise but Superman's Xray vision as well. He ain't gonna steal MY intellectual property!

Steve Ahola

[Steve A.]

Sad story about copper foil tape and pickguards... I used to get 4x10 sheets of copper foil tape from electronics parts houses. Thinner than the StewMac variety but a bigger problem was that the adhesive was not electrically conductive.

I was shielding the huge pickguard on a 2001 MIM Tele Thinline and tried butting the sheets together to establish continuity but no such luck. So I thought I could get away with a few very tiny solder tags. Yikes! The pickguard buckled a bit from the heat.

I traced the outline of the pickguard with screwholes on newsprint figuring I might eventually run into a replacement. No such luck. For an OCD-elightful person like myself that guitar was always tainted.

Steve

[Steve A.]

Aluminum a PIA for pros too. All I can see, it's a poor excuse for those who will not bother to source copper, and/or afraid of soldering. Only excuse left is if you live in a part of the world where copper foil, sticky or not, is just plain unavailable. When I see someone's bothered to make a video, and uses patches of electrical tape to stick bits of aluminum foil together, this has got to be a joke, right? "How to do a half ass job."
Copper IS the solution. Period.

Although I generally avoid it conductive carbon paint is almost as good as copper... unless you are building Faraday cage! After 3 or 4 coats I would clear coat it to make sure the carbon couldn't flake off or short something out.

Steve

P. S. The original carbon paint in the 70s used an MEK base and the instructions said to mask off the holes for the pots. I didn't have any masking tape but I figured that two layers of Scotch Magic would be just as good. Well, it wasn't and the finish around the knobs on my brand new 1976 LP Standard was a bit mottled. Ouch!

[Jason Rodgers]

OK, if it's wide enough to do the job without seams.
I've never had luck maintaining long-term continuity across aluminum tape seams.
Tabs, schmabs, within a day oxide layer raises resistance to "not connected".
YMMV.

So, if I buy a roll of aluminum foil tape, and it sits in my shop for a couple years (because I'm not building that many), how oxidized was the tape when I bought it, and how much more has it oxidized while sitting there? And if I shield a cavity with overlapping edges and a cover touching those tabs under the screws, how much more oxidation will develop and open those joints? I'm going to listen to folks with electrical and chemical experience, but it doesn't seem like such a liability.