Conductive paint question

[catalin gramada]

Hello. Want to shield a guitar cavity with conductive paint. Does any conductive paint related for the job ? For instance found a product which is advert it not contain any metal. Still conductive recommended for electrical applications. Think is carbon based paint or what ? May I add aluminium oxide or some on it to make it usable please ?Thanks.o

[Helmholtz]

Like most metal oxides aluminum oxide is an isolator (not conductive).

Carbon based shielding paint should be fine. Doesn't need to be highly conductive like metal foil for electrical shielding.

[catalin gramada]

Thanks. What about a zinc based paint called for "cold galvanising". Don't find any specs if is conductive or not, just to protect against rust. made from 99% pure Zn. Have no ideea if may be used for shielding...

[Chuck H]

I can't say about zinc paint except that zinc is non ferrous and therefor not magnetic, like carbon. I wouldn't expect any benefit over the carbon based products.

I've never tried the conductive paints for body cavity shielding on guitars but many manufacturers have gone that way for a long time. And I've never done a side by side comparison of copper foil and conductive paint. But something in my core says the copper foil should perform better.?.

My only experience with conductive paint was a job I did for a customer that lived near a cell tower. They were concerned about emission from the tower melting their brains. So they had me coat their home in a conductive carbon paint prior to the actual house paint. Applying the conductive carbon paint includes "grounding" it. Which was provided as a kit with conductive paste, a plate and a spike to pound into the dirt. So...

Just because I'm a skeptic by nature I brought my DMM to the site and tested the actual conductivity of the material (which was applied at the recommended mil thickness). With my arms spread as far apart as possible and a probe in each hand I consistently measured 51 ohms or less with a half dozen attempts. I thought that was pretty good. That said...

How much the magnetic properties of guitar shielding materials might matter or be beneficial I can't say. But as to zinc or carbon, niether is magnetic anyway.

[Mick Bailey]

Cold galvanizing paint may be conductive, but could depend on the brand. To work properly in its intended use it has to be in electrical contact with the steel substrate just like the zinc sacrificial anode on a steel boat hull. The only way to find out is to spray or paint a test strip and measure the resistance.

I've measured the resistance of some Fender guitars and whilst I can't recall the exact figure it was in the Kohm range (rather like the carbon shielding on cables).

[Chuck H]

Cold galvanizing paint may be conductive, but could depend on the brand. To work properly in its intended use it has to be in electrical contact ...

Right! Some galvi paint products "look" like galvi but have a type/amount of ploymers that prevent good conductivity. In order to be properly conductive any conductive solids particles (zinc, carbon, silver, etc.) have to be in contact with each other. So the actual ratio of those solids in the paint and the nature of the binding polymer greatly affects conductivity.

[Tom Phillips]

A high end approach to conductive paint is to use a silver based product. A down side is that it is very expensive. Therefore, I'm adding this comment for completeness and not as a recommendation that you should, or need to use it, for your project. I worked in an industry that used silver paint to put conductive tracts on piezoelectric ceramic. The lead wires were then attached by directly soldering them to the silvered stripes using silver bearing solder.

Anyway, it's a cool product but know that a 12ml bottle of the stuff would cost $75 to $100. The cost has really gone up since I used it. Wish I would have saved some when I had the chance. It's useful for special projects such as adding a tap to a pot track.

[Chuck H]

A high end approach to conductive paint is to use a silver based product. A down side is that it is very expensive. Therefore, I'm adding this comment for completeness and not as a recommendation that you should, or need to use it, for your project. I worked in an industry that used silver paint to put conductive tracts on piezoelectric ceramic. The lead wires were then attached by directly soldering them to the silvered stripes using silver bearing solder.

Anyway, it's a cool product but know that a 12ml bottle of the stuff would cost $75 to $100. The cost has really gone up since I used it. Wish I would have saved some when I had the chance. It's useful for special projects such as adding a tap to a pot track.

And, again, the level of conductive solids (and in this example "solderable" solids and heat resistant polymers or other binders) greatly effects the application. There are, indeed, silver paints with actual silver solids that look great but have too much non conductive or non heat resistant polymers in their matrix to be properly conductive or solderable. Products sold as "conductive" are engineered for such. And there's no substitute for testing.

[catalin gramada]

So, "cold galvanising" have so much in common with galvanising as "artificial leather" have with the leather ? Is a simple paint, nothing more nothing less ?

[Mick Bailey]

It comes down to the product. I have four different types of cold galvanising - two brush-on, two spray cans. I don't know about the sprays, but the brush types I have are no better than any other paint as they have the zinc suspended in an alkyd binder. If I get chance today I'll do a couple of test strips with the spray cans and measure the resistance. I think if you got an industrial product it may be conductive.

[nosaj]

so is there a problem with using copper tape? It works very well and easy to install and you can solder to it.
nosaj

[Helmholtz]

so is there a problem with using copper tape? It works very well and easy to install and you can solder to it.
nosaj

Nothing wrong with copper tape. But conductive paint works just the same.
No need for very low resistance as there are no significant currents.

Neither provides magnetic shielding, that's why there are humbucking PUs (and dummy coils).

[nosaj]

When you coat the pickup cavity and the back of the pick guard is that not in effect a faraday cage which block electromagnetic fields?
nosaj

[Helmholtz]

When you coat the pickup cavity and the back of the pick guard is that not in effect a faraday cage which block electromagnetic fields?
nosaj

Doesn't work for audio frequency magnetic fields.

[nosaj]

Doesn't work for audio frequency magnetic fields.

Well you don't do it for audio frequencies i thought it was done to like block the effects of noisy devices like flourescent lights entering the audio chain in a single coil pickup set.
Am i wrong in this thinking?
nosaj