2014-07-21 (M) Conductive Paint Experiment

Commercially available conductive paint was tested by stirring and painting lines in the same manner as the other samples. The commercially available conductive paint was much more liquid so it produced thinner traces. All traces were dried for at least five hours in the order to test their resistance as it would be in a finished project. Each substance was measured again with fixed-width probes. Close-up pictures were taken of each sample using a macro lens. The lens has a very shallow depth of field which is not flat so the samples are not entirely visible. Acrylic paint with graphite powder is the most conductive sample in this experiment when painted in a line like a circuit trace.

Thick line
Thin line
18.8 KΩ
10.5 KΩ
11.2 KΩ
Titebond III
115.1 KΩ
75.2 KΩ
9.9 KΩ
Acrylic paint
1.8 KΩ
60 Ω
1.161 KΩ
1.490 KΩ
338 Ω
26.1 KΩ

Sampling surface

Glue-All samples being tested

  Titebond III samples being tested

Acrylic paint samples being tested

Commercially available conductive paint samples being tested

 Close-up of Glue-All and graphite sample

 Close-up of Titebond III and graphite sample

 Close-up of acrylic paint and graphite sample

 Close-up of commercially available conductive paint sample

Stirring the commercially available conductive paint to show viscosity

To do:

  • Translate to an Instructable 
  • Devise a distribution method

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  1. Did you do any testing with different COLORS of acrylic paint? I don't know what they make the pigments out of, but isn't it possible that some are more conductive than others? Some might be metal-based.

  2. Also, some very inconsistent results in readings.

    Glue all resistance goes up only 6.6% from thick to thin line.
    Tite Bond III actually does DOWN with a thinner line. Doesn't make sense.
    Acrylic goes up by 1935 times from thick to thin line.
    Wire Glue goes up by 7700 times from thick to thin line.

    Since in every case the conductive medium is graphite, I would expect more consistent results. I suspect the Titebond results are reversed.

  3. I only tested a single color of paint which I had on hand but I suspect some metallic sheen paints would conduct differently. If I were going to make a large batch I would likely choose those paints over plain colors now that you mention it. You got my brain ticking again and here I thought I was done with this project.

    The pictures for the readings tell the story and you are right that the test results didn't make logical sense. All I was looking for was for was a rough idea of which medium conducted well while maintaining a usable consistency. The paint stood out as a clear winner so I called it. The tests I ran were not scientifically rigorous in fact I would put them on par with a high school science experiment.

  4. I was thinking more in terms of normal paint pigments based on metal compounds, not metallic ones. For example, cadmium, antimony and chrome compounds are used for different colors. I can't take that information too far because I'm not really knowledgeable about pigment chemistry. But the thought occurred to me the pigment might matter. I don't even know if any of those compounds are even conductive even though they are metal compounds.

    Anyway, you're the first guy I know who has actually done anything about this application, and I applaud you for that.

    I've been a ham for 57 years and spend most of my time designing and building circuits, not yakking on the radio. So the idea of a reasonably conducting paint looks like an interesting direction to spend my time on.

    1. I see what you're saying. I'm probably less of a chemist than you but I think some reds may use iron oxide as a pigment and that has a lot of potential. At least it would when I applied voltage. Sorry, I couldn't resist that joke. Or that one.
      I wonder how the hobby store would feel about me opening all their paints and dipping my probe leads in. They probably wouldn't be too keen on it and I don't think paint inspector is a real thing.
      My analog/digital communications teacher was a HAM operator and had been for years. When they finally dropped the necessity to learn Morse Code he really pushed us to get our licenses. Sadly I didn't and now the hack space I go to has a HAM station I could use if I were licensed.
      If you make a winning recipe I will gladly link from this site. Good luck.

  5. Not too late, Brian. A couple weekends of study (mostly FCC regs and a little theory), and take a test with a Volunteer Examiner through any of a number of ham radio clubs, and you're licensed. Your hack space guys will know exactly what you need to do. No code, but lots of new hams are discovering code is fun and VERY practical for weak signal work because of very low bandwidth, and the fact it is the only digital mode that the human brain can copy. Anyway, glad I found your blog and your work with conductive paints.

    When I give it a try, I'll post here as I don't have a blog. You can use the info any way you choose then.

  6. Maybe you can give the sales pitch for ham radio to me and anyone else following this comment thread. The internet can provide all the communication I need so what's the appeal of doing it over analog?
    I have heard that when tragedies strike that civilian radio operators are some of the first to respond and instrumental as a communication hub. To date that's the most appealing thing I've heard.
    It would be awesome if you found a recipe that tested better than what I've done and I think the readers would appreciate another set of hands testing!

  7. Those of us who fly RC sailplanes could easily put in motors and bore holes in the sky, but we'd probably fall asleep out of boredom. My guess is that HAM operators would feel the same way about the internet. I imagine they like playing around with antennas and mastering all sorts of technical info. Somewhere I have a stack of radio contact cards that my ex's father gave me. Rather interesting, from a bunch of different far away places.

    On the conductive paint, my guess is that a lot of the resistance is at the junction between the voltmeter probe and the material. You've got a variably shaped surface with very little contact area. It's also not clear that the proportion of graphite to paint is constant all the way through the material. Maybe in some cases the paint/glue comes to the outside. You might try making some standard size copper pads and running tracks between them. Or figure out how to make a really consistent, large surface, and use a good sized chunk of metal placed on it instead of a voltmeter probe. Maybe you can just built it up thick and sand it down flat?

    Curious as to exactly what sort of graphite you're using. (Brand, composition, etc.)

    Someday, I am going to get my van de Graaff generator going again, and it needs a better terminal. Metal spinning is kind of expensive.


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