Shielding Paint

BillDL · August 2023

I have two finished electric guitar bodies for single coil pickups. I usually use self-adhesive copper shielding tape if I decide a guitar might be worth spending some extra time on or actually benefit from shielding, but it's fiddly to use so I decided instead to buy a small tine of "Rustins G Shield" water based EMI shielding paint from Northwest Guitars. I just decided to shield them while I was at it whether or not they might need it, and the paint seemed to be a much cleaner and less fiddly option.

Rustins product page and the Product Data Sheet PDF.

The label iterates what is on the Rusin's page, i.e.

"Rustins G-Shield is based on a high-quality water-borne, cross-linking acrylic resin containing Natural Exfoliated Graphene to provide reliable shielding from high-frequency electromagnetic fields and low-frequency electrical fields. G-Shield is solvent free with low-emissions and has lasting corrosion resistance as the paint contains no metal particles, the graphene in the paint prevents the formation of corrosion on metal surfaces."

I've never used shielding paint like this before. I used to have an aerosol of protective zinc paint that was conductive and worked well for shielding but it never really formed a hard smooth surface and dried kind of "powdery", and I once used a silver paint-on shielding that felt "metallised" once dry. This Rustins paint is jet black, goes on smoothly and seems to dry to a nice matte black, but when it is touched with anything, the graphite rubs off exactly as it would if you scribbled on paper with an HB pencil and then rubbed your finger over it and it leaves shiny spots on the paint. It says in the blurb that it can be used under emulsion paint, but I'm not entirely convinced that other paint would adhere properly to it's slight slipperiness.

Additionally it isn't very electrically conductive. When using a digital multi-meter in continuity mode I get the beep when I'm testing conductivity and the probes are quite close together, but from one end of a continuous "strat" cavity to the other I don't get a beep at all just like THIS guitar builder discovered. I notice that the video made by Rustins is demonstrating mobile phone signal blocking or "electro smog shielding" using a cardboard box rather than guitar shielding, so electrical conductivity and grounding isn't a consideration in the demonstration.

My understanding of shielding in a guitar is that it has to form a continuous conductive path throughout all the surfaces that are shielded, and this is grounded. Clearly this paint isn't going to be as good in the conductivity aspect as copper foil, but is it going to work as intended?

Has anybody used this Rustins product, and what are your thoughts about it or about paint-on shielding in general?

Sporky · August 2023

I've not used the Rustin's, but I did buy a tiny, very expensive tub of shielding paint a few years ago for my electric cello - it was picking up a lot of noise from the crap dimmers our electrician installed. That worked a treat - from almost unusable to virtually silent. I'll see if I can find what it was - only needed a small fraction of the tub, for a cavity about the size of a LP's.

BillDL · August 2023

Thanks @Sporky. ; This tin of Rustins paint was only 125ml for £8 and I've only used a little bit of it, so perhaps the much more expensive stuff in a tiny container would have been a better choice. I've just given it a 2nd coat to see whether the electrical conductivity improves. If it doesn't work very well I'm not going to spend time or money buying another tin of some other paint though, because it probably wouldn't stick anyway and I really need to get on with assembly. I would be curious to see what the conductive substance is in the paint that you used, but don't spend a lot of time raking around for it.

Sporky · August 2023

Pretty sure it's graphite. The multimeter read several/many ohms, but it was still jolly effective.

BillDL · August 2023

I did see mention of the resistance in the video by the German sounding guy that I linked to. I must check that on mine when it's dry.

Sporky · August 2023

I've also used the spray stuff - possibly the same you mentioned. That worked too, but I think I liked the brush-on stuff better.

BillDL · August 2023

I've had a look around and I see that places like Touchstone Tonewoods, David Dyke, and many other musical instrument specialist suppliers of wood and parts sell the same Rustins paint, so I can only assume it must be effective. I've also noticed, while comparing the ingredients of other shielding paints, that "graphite" or "carbon graphite" are common to them all. Rustins fancy "natural exfoliated graphene" expression explained - 2D flat particles rather than 3D crystalline.

Simo · August 2023

I've used the G-Shield on my last few builds and have had no problems with conductivity.. in fact it's probably the best carbon based shielding paint I've used. I typically apply 2 coats, but it normally passes the beep test on the multi-meter after just a single coat.

The only thing I can suggest is to make sure you stir it REALLY well, as the carbon sinks to the bottom of the can.

FelineGuitars · August 2023

I have been using the G Shield for about the last year and it seems to work well

I have a tin of the nickel screening paint that is going spare - nearly a litre if someone is interested as seem to be using the G shield most of the time now

BillDL · August 2023

Thank you @Simo and @FelineGuitars

You are bang on about the stirring and the carbon/graphite sinking Simo. I did stir the tin for a while before using it for the first coat but I then took about 15 or 20 minutes re-sticking some masking around the cavities on the guitars and going for a fag before painting. Before I applied my 2nd coat I shook the tin and then stirred it to release the bubbles. I stirred it again half way through doing each of the bodies and worked quickly. This time the electrical continuity is good across the entire area that I painted.

BillDL · August 2023

@Simo and @FelineGuitars - I've just finished wiring one of the guitars that I shielded with Rustins G Shield, and I have to say that I am really pissed off with it. I don't know how you both deal with the shiny black graphite that rubs off onto the cables, pots, capacitors, plastic parts like pickups and surrounds, the guitar body, and anything else you handle or touch after getting it on your hands. The mere act of pulling wires through the connecting holes from control cavity to pickup routs to switch cavity in the top bout left my hands dark grey. It doesn't come off hands very easily (OK, I should have worn latex gloves). I had to repeatedly scrub them with washing up liquid because ordinary soap hardly touches it and white basins have to be scrubbed with a pot scouring sponge after washing your hands. I remember using aerosol Molykote on the screws and shafts of lifting actuators when I worked in an engineering shop floor. It got everywhere and I had to wear a Tyvek suit and disposable gloves. The stuff that rubs off dried G Shield is quite similar.

I did the bulk of the harness on a drilled-out plywood template as I always do, but there are obviously wires that need to be soldered to the harness next to and inside the control cavity. Touching the wires to solder them after they've been anywhere in the shielded cavity means the stuff rubs off the wires onto your hands. I ended up getting the graphite onto an old set of cream DiMarzios and the cream surrounds when I put my hand over them to flip the guitar and pull the wires though to the cavity without realising I had some of the graphite on the heel of my hand, and I've had to use a toothbrush and alcohol to try unsuccessfully to remove the grey shiny marks. I will need to use Brasso to rub some areas of the lacquered body where I touched it without thinking.

This stuff is filthy to work with and I won't be using it again. Unfortunately I have another two bodies to wire up that I shielded with it. I hope I don't have to do any re-work on the wiring at a later date.

Deadman · August 2023

I spray my respective colour straight over the top of that gear, Bill, get it on before painting effectively, so I’ve never noticed that it comes off so easily. Might be something you could do to alleviate the problem along the line? That is of course if you decide to use the filth again

I’m sure it won’t affect the quality of the final outcome anyway, as your stuff is always top notch

SimonRF · August 2023

The Rustins stuff shields well but is, as you've found, a bit messy if left unsealed. We used to do a solvent based one but can't get it any more, and it seemed to stay put itself a bit better.

A cleaner alternative would be copper shielding tape or sheets, and it has the advantage of being shiiiiiiny ooooooh.

ICBM · August 2023

I really don't like shielding paint at all. It doesn't seem too bad when it's used like Fender do, under the normal finish, but even then it has a tendency to rub off where it's exposed, and I don't think it does a very good job. I've done dozens of jobs to stop noise in guitars which are supposedly shielded with it, by adding proper copper foil shielding, and in every case it's proven that the paint shielding is some variation of not very good to completely useless.

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