Grounding Paint

[Mark Hammer]

Keep in mind that it is paint that dries. This means that layers can be built up. And, just like wire, the thicker it is, the lower the resistance.

Is it a panacea? I think not. But it IS useful in many places that are difficult to apply other forms of shielding to. For example, I've used copper shim material, cut to size, not only for control cavities, but for providing some shielding to the inside of plastic effects pedal boxes. I cut the piece to size, pop holes in the appropriate places, and the pots and toggles hold the material in place against the chassis. What's nice about it is that you can solder to it. But I imagine there are plenty of places where it would be hard to fit, or provide incomplete shielding, or simply be dangerous because of sharp edges.

You can't solder to conductive paint, but you CAN sink a screw with a washer into it and solder to the washer.

[big_teee]

I sent an email to their parts department.
I'll let you know what they have available in the shielding paint?
T

Here is Peavey's reply!
"We do not have this any longer. It has been years since we've even used it. You can go to a parts warehouse like Digikey and see if they have this for you to purchase."

[Leo_Gnardo]

Who stirred up this can of conductive paint big_teee, after all these years? Here's a couple t'ings to t'ink about. Assuming the paint works, and works well enough for the application - the paint layer you put inside the guitar has to be grounded for it to work as shielding. It might happen "by accident" with potentiometer frames pressing against the paint (perhaps aided by star washers). Or on purpose, like running a wire from the guitar output jack ground to a screw-mounted solder lug, again pressed into the paint by pressure from the screw. Conduction integrity can easily be checked with an ohm meter. You should get a reading on an ohm meter, with one lead on output jack ground and the other anywhere on the paint, of a couple hundred ohms up to a couple thousand. That will do for shielding.

If you DON'T ground the conductive paint layer, it CAN act as a noise inducing item.

Don't leave signal-connections accidentally leaning against the paint, anywhere. If you wonder where your signal went, it's shorted out by black cement.

Some advice I got from John Suhr, a long time ago: Conductive paint must be fresh for it to work well. Buy the freshest stock you can find, use it right away, toss it out after 6 months. That was 25 years ago. Perhaps conductive paints have gotten better. Has anyone else found their shielding paint going dodgy in storage?

Personally I use copper foil. Nothing like completely mummifying the inside of a guitar with soldered strips of copper.

[Enzo]

Of course all those don't let a lead touch it or leaving it unconnected warnings apply to metal, like foil, as well.

[big_teee]

Thanks for all the help guys.
I rewire many guitars a year.
In a small body cavity, like my SG, it has 4 Pots, a Switch and a Guitar Jack all in about 5 inches of each other.
I think it should be common to ground, no lugs, close enough on the ohm meter.
I only put foil in or on big areas, too much trouble for cavities, for the little gain.
Talk about shorting, it is much easier to do with foil, if the foil gets loose.
Anyway, the proof is in the Pudding.
I finally got it all rebuilt today and much better, and much quieter.
I ripped all the wiring and old pots out.
Tried something different, I put 4 Alpha 500k B linear Solid shaft pots in it, that I have had a long time.
Used shielded wire on everything.
Like I mentioned earlier this is a test mule guitar, strictly for testing pickups.
With the linear pots, I sure like them better in my Lefty, than using Audio taper Pots wired backward taper.
It is much quieter Since the rewire.
Now I'm back to looking for some more paint at a good price.
I may try the 1/2 pint of StewMac Paint.
T

[Paleo Pete]

I use heavy duty aluminum foil for pick guards, I did one cavity with aluminum tape. Same paper backing stuff mentioned above. Use spray glue and spray BOTH surfaces, not just one, and the foil will stay put. My Squier strat was factory sprayed but little on the pickguard, I made sure both were grounded and foil on the pickguard, it's quiet as can be. Foil has stayed put on the pickguard with no problems for about 8 years now.

Leo brought up a good point, the cavity must be connected to the ground somewhere. I used the same ground wire going to the bridge, wrap it around the corner and add some tape. Mash it in good. (with just a finger though) Mask and spray seems to be the best way to go.

I've done every guitar I have except the Cort CL1500 hollow body, don't want into that nightmare...the Harmony Bobkat was tricky, no metal bridge plate, I had to drill a hole with an 18 inch long drill, (nothing else would get in there at an angle and not chew up the body with the drill chuck) and run a wire so it contacted the pickguard and string claw. Bridge is wood and slides for intonation. Then had to run it to the cavity...

I've seen the arguments about whether it works or not, let your ears tell you the story. It does make a difference...don't expect it to eliminate all noise, but most of it will go away.

An off topic tip for you too, when you replace everything, ditch the springs on the pickup adjustment screws and use surgical tubing. It works great.

[big_teee]

I still like the paint for cavities.
Works just as good IMO as Foil, and is much much easier to install.
Guitar companies have been using it for years in cavaties.
Good enough for them, it's good enough for me.
Like I said I do like heavy aluminum foil for pickguards, and cavity covers.
I do like the rubber tubing for pickups on pickguards.
I like heavy springs for Humbuckers in pickup rings, especially if the baseplate is the long legged variety, that require long Screws.
T

[solarbass]

I work on EMI/EMC control sometimes and design & test products in shielded rooms for emitted and accepted RF interference.
We use 3M Copper tape (like 3M 1182) in our efforts to shield things (emissions and accepted).
Paint can work but I would think it would be effective at a narrower bandwidth than copper tape and with less attenuation of the unwanted signals.
I have seen plasma coated plastic enclosures, they can work if done properly.

For Cu tape to work well in a wood or plastic guitar you need to cover the whole inside of the cavity, and burnish the tape down where it overlaps the next piece.
I would put in little dots of solder to connect one tape piece to the next, for longevity. Use coax out to the pickup(s).
Tape the lid too, inside, and solder a short wire to the body from the lid to give it a ground path.
Sometimes the cable jack body can be tightened into the copper tape but a ground wire soldered on or attached with a screw lug is preferred.
You are making a Faraday cage out of the tape. Effective over a wide range of frequencies, up to the microwave spectrum if done right.

[big_teee]

I work on EMI/EMC control sometimes and design & test products in shielded rooms for emitted and accepted RF interference.
We use 3M Copper tape (like 3M 1182) in our efforts to shield things (emissions and accepted).
Paint can work but I would think it would be effective at a narrower bandwidth than copper tape and with less attenuation of the unwanted signals.
I have seen plasma coated plastic enclosures, they can work if done properly.

For Cu tape to work well in a wood or plastic guitar you need to cover the whole inside of the cavity, and burnish the tape down where it overlaps the next piece.
I would put in little dots of solder to connect one tape piece to the next, for longevity. Use coax out to the pickup(s).
Tape the lid too, inside, and solder a short wire to the body from the lid to give it a ground path.
Sometimes the cable jack body can be tightened into the copper tape but a ground wire soldered on or attached with a screw lug is preferred.
You are making a Faraday cage out of the tape. Effective over a wide range of frequencies, up to the microwave spectrum if done right.

I do use heavy foil on the cavity cover, and pickguards, but for the cavity, I still prefer the paint.
Especially on a test guitar, where you're in and out of it often replacing pickups, and the cavity can be touched up with the paint, when necessary.
But, Like I said, whatever one likes and whatever meets your needs.
GL, YMMV,
T