I'm looking for inexpensive conductive paint...

[Few]

As I continue (endlessly) to brainstorm ideas for a segmented stator construction that will provide more uniform directivity, I keep coming back to the idea of applying conductive paint to an insulating stator. The idea would be to paint a narrow vertical stripe for a tweeter and wider ones for midranges etc. (an updated version of Wagner's approach).

McMaster-Carr has perforated plastic sheets that look promising but I'm still looking for a source of relatively inexpensive conductive paint that will adhere well to the plastic. Silvaspray (link) looks like it would work but it would be expensive by the time decent sized stators were coated. They also don't recommend brushing it on and I don't have a suitable sprayer. I've tried following up on an Electrolube suggestion (link ); they supposedly make a nickel-based coating that costs less than silver-based coatings. So far I haven't yet been able to identify the right product on their website.

Does anyone have any experience with this stator construction approach or a suggestion for relatively inexpensive conductive paint suitable for plastic?

[Cal Weldon]

I have no experience with stator construction but I wonder about the aluminum paint used on roofs in place of gravel. If it works, it would cetainly be cheap enough. Call your local roofing supply shop and see what they have. Maybe even a sample for you to try.

[Bazukaz]

Amuminium paint is a mix of oxidized particles.as far as i know , it should not be very conductive.But there are other cheap paints, like chome paint... I am not really sure about this.

Regards,
Lukas.

[lndm]

I believe the silver paint used to repair automotive rear windscreen demister grids is brushable.

[Mike Beck]

You might try Aquadag or one of the similar products from www.achesonindustries.com

[moray james]

Consulting your local plate service? I should think that shops that plate even chrome (like on yur bumper) would be able to help but certainly any shop that builds PCB's would be able to plate just about any metal on any surface that you like with precission. Just a thought. Regards Moray James.

[Calvin]

Hi,

even though it seems a good and easy way to paint an insulating sheet, I think it has some major drawbacks against other solutions.

You don´t know -and very probabely the paint manufacturer too- how the paint behaves when high voltage is applied.
You have to be extremely careful when coating the plastic that no paint runs into the holes...I can only think of overhead rolling...but still
it´d good to insulate with a acrylic or polyurethane paint too.

I´d try to experiment with copper plated printed cardboard. Epoxy FR4 has good properties (epsilon: 4-5, R: app 10^12..10^14Ohms, high dielectric strength: ~40kV/mm and You can get it cheap everywhere)

You may easily etch holes in the copper ( and You´re not bound to round holes!) and have holes drilled in afterwards that are concentric to the copper holes but slightly smaller in dimension. Coating the copper side with an insulating paint, or sealing it with a second printed board You´d have a stator that would work flawlessly.

jauu
Calvin

[Few]

Thanks very much for the suggestions. Aluminum quickly develops a native oxide when exposed to air so I think aluminum article-containing paint is unlikely to be very conductive. The silver paint used for rear window defrosters (which is pretty similar to the stuff used for electron microscopy sample preparation) would probably work but it might be cheaper just to ask Martin Logan to drop off some of their latest products!

It may turn out that trying to use conductive paint simply isn't competitive with the other approaches. However, there is at least some evidence that the conductive paint approach works. Neil McKean, in fact, promotes it as his preferred method, so I take that to mean it's been tried and shown to work. Unfortunately, I still haven't been able to idenitfy which Electrolube product he refers to on his site and the email address listed there no longer works.

So, I remain interested in at least thinking about this approach. I may ultimately join the wire stator brigade but before I start designing in detail I want to be confident I've adopted the approach best suited to my goals. If there are more ideas or suggestions out there, I'd very much appreciate hearing about them.

Thanks again for the thoughts expressed so far.

[moray james]

If you find an aluminum paint I would not worrie about it forming oxide. At best only the top layer may develope oxide as the paint sets up as that will be the only part exposed to air. Further as mentioned colloid suspensions have been used for comercial designs (Quad) and that is not all that concuctive. At the voltages we are talking about the coating does not need to be very conductive and resistive coatings will work well. You might consder conductive inks or even finding a good paint that bonds well to your substrait and doping it with carbon black. I think the key is to keep things on a try it and see basis rather than getting to scientific about it. Most commercial products were developed by people like you looking for the cheapest easiest to find materials at hand. Paul Voight who designed the Lowther driver was considering what to use for cone material which had to be thin light and stiff. While looking through his reference files he had a manilla folder in his hands and thought that it felt about right. With a pair of sissors and some tape he made a cone. That was what they went into production with. Good luck regards Moray James.

[BillH]

Few writes:
Does anyone have any experience with this stator construction approach or a suggestion for relatively inexpensive conductive paint suitable for plastic?

Few, the conductive paint method is described in Ronald Wagner's 'Electrostatic Loudspeaker Design and Construction' book. He uses painted strips from 1/4" to 4" wide with resistors to roll off the low frequency of the smaller strips. I liked his design, but could never figure out how to get or build the perforated substrate.

The conductive paint he uses doesn't seem to be available anymore, but here's an alternative. It's a copper based latex paint with <0.3 ohm/square at 1 mil dry film thickness. US$30 for 4 oz. should cover about 20 square feet.

Few writes:
McMaster-Carr has perforated plastic sheets that look promising

What's the McMaster number for the plastic sheets? I'd like to take a look at them.