how to mix graphite powder to get shielding paint

Pickups, magnets, microphones, amps, speakers, cabs, whatever...

how to mix graphite powder to get shielding paint

Postby Greg Martin » Sat Oct 31, 2015 1:42 pm

I was given a pound or 2 of graphite powder,and some one said shielding paint could me made. What binder/solvent would be best to make it brushable and to to keep conductivity?
Greg Martin
 
Posts: 302
Joined: Thu Feb 23, 2012 7:18 pm

Re: how to mix graphite powder to get shielding paint

Postby David King » Sun Nov 01, 2015 7:15 pm

I don't think I'd waste a lot of effort on this but you could try with some water based varnish and see if you can maintain conductivity. I remember hearing from someone who had tried this and given up on it.
David King
 
Posts: 2428
Joined: Sat Jan 07, 2012 10:01 pm
Location: Portland, OR

Re: how to mix graphite powder to get shielding paint

Postby Daryl Kosinski » Sun Nov 01, 2015 7:21 pm

Daryl Kosinski
 
Posts: 97
Joined: Sat Oct 12, 2013 11:14 am
Location: Fultonville, NY

Re: how to mix graphite powder to get shielding paint

Postby Greg Martin » Tue Dec 01, 2015 3:50 pm

well right now I have a large bottle of powder, i dont have copper foil, so Id like to make this resource work.wterbourne finish or maybe shellac or hide glue will be my first testing agents l thanks for the tips.
Greg Martin
 
Posts: 302
Joined: Thu Feb 23, 2012 7:18 pm

Re: how to mix graphite powder to get shielding paint

Postby Andrew Porter » Thu Dec 31, 2015 2:33 pm

How about applying a good coat of paint dump in the powder. Empty when dry. Drive a screw through with the grounding wire.
World's Second Finest Maker of Expensive Sawdust
User avatar
Andrew Porter
 
Posts: 87
Joined: Sun Jan 08, 2012 8:49 am
Location: The Banks of Sleepy Creek, NC, USA

Re: how to mix graphite powder to get shielding paint

Postby Eric Baack » Thu Dec 31, 2015 3:58 pm

you can also get foil tape from ebay and amazon for pretty cheap. I've checked continuity on it through the adhesive and it checks out.
Eric Baack
 
Posts: 615
Joined: Thu Dec 27, 2012 4:28 pm

Re: how to mix graphite powder to get shielding paint

Postby Dan Smith » Fri Jan 01, 2016 1:00 am

We used zinc paint in the old days to coat electronic frames for grounding.
I use copper foil tape these days, easy to apply.
Ever-body was kung fu fight-in,
Them kids was fast as light-nin.
User avatar
Dan Smith
 
Posts: 328
Joined: Mon May 18, 2015 9:33 pm
Location: Texas

Re: how to mix graphite powder to get shielding paint

Postby Greg Martin » Sun Jan 24, 2016 2:39 pm

Ok thanks anyway guys Like I said Ive bought and used aluminum and copper shielding tape for years,but was given a pound of graphite powder and wondered what the liquid agent was to make it paintable like stewmacs !!! Ive got it, just need to know what its good for. Im going to try waterbased finish and maybe shellac as a liquid agent as a first testing. See what happens.
Greg Martin
 
Posts: 302
Joined: Thu Feb 23, 2012 7:18 pm

Re: how to mix graphite powder to get shielding paint

Postby Gregory nangle » Sat Feb 06, 2016 9:11 pm

the best thing to do as a graphite expert is to use a mixture of isopropyl alcohol and graphite powder (be sure the powder is truly powder) spray this on and then follow that after it dries with a coat of shellac thinned a bit with denatured,they both use the same airborne finish to dry.must be sprayed! the first coat or two of your mixture will pull off the surface until its sealed in with the shellac.
Gregory nangle
 
Posts: 35
Joined: Fri Jul 31, 2015 12:07 pm

Re: how to mix graphite powder to get shielding paint

Postby Gregory nangle » Sat Feb 06, 2016 9:29 pm

you could also use 'acrylic medium' mixed with graphite powder to brush it on ,thats a more robust finish and probably easier to apply.
Gregory nangle
 
Posts: 35
Joined: Fri Jul 31, 2015 12:07 pm

Re: how to mix graphite powder to get shielding paint

Postby David Schwab » Thu Apr 07, 2016 1:43 pm

Gregory nangle wrote:the best thing to do as a graphite expert is to use a mixture of isopropyl alcohol and graphite powder (be sure the powder is truly powder) spray this on and then follow that after it dries with a coat of shellac thinned a bit with denatured,they both use the same airborne finish to dry.must be sprayed! the first coat or two of your mixture will pull off the surface until its sealed in with the shellac.


Wouldn't the shellac act as an insulator? How are you going to make an electrical connection with the paint?

Personally I never found the carbon based paints to work very well, and in most cases there's very little reason to shield control cavities, which is what it's mostly used for.
User avatar
David Schwab
 
Posts: 69
Joined: Sat Jan 07, 2012 6:59 pm
Location: Staten Island, NY

Re: how to mix graphite powder to get shielding paint

Postby Hans Bezemer » Thu Apr 07, 2016 2:03 pm

You could make Indian / Chinese ink with it: http://www.ehow.com/how_7370727_homemad ... n-ink.html
I've used Indian ink to stain wood and it shielded well.
User avatar
Hans Bezemer
 
Posts: 373
Joined: Sat May 26, 2012 1:01 am
Location: The Netherlands

Re: how to mix graphite powder to get shielding paint

Postby Jason Rodgers » Tue Apr 12, 2016 12:18 am

Hans Bezemer wrote:You could make Indian / Chinese ink with it: http://www.ehow.com/how_7370727_homemad ... n-ink.html
I've used Indian ink to stain wood and it shielded well.

Hmm, so you're saying the lampblack in India ink has enough carbon to shield? Can you put a meter on it to show conductivity for grounding? What sort of resistance does it show across a cavity?

If you're going to attempt to mimic India ink, then the traditional binder was hide glue (or so says wikipedia https://en.wikipedia.org/wiki/India_ink).

The graphite grounding paints are pretty nasty, especially if you're trying to go low-VOC in your finishes. India ink would be a hugely less toxic alternative, if it worked as a shielding paint.

EDIT: After reading the wiki article in length, I see that it is in fact used in some shielding applications: Once dry, its conductive properties make it useful for electrical connections to difficult substrates, such as glass. Although relatively low in conductivity, surfaces can be made suitable for electroplating, low-frequency shielding, or for creating large conductive geometries for high voltage apparatuses. A piece of paper impregnated with India ink serves as a grid leak resistor in some tube radio circuits.

I don't understand the electrical engineering application descriptions, but I suppose "relatively low in conductivity" excludes it from use as a cavity shielding paint.
-Ruining perfectly good wood, one day at a time.
Jason Rodgers
 
Posts: 1553
Joined: Fri Jan 06, 2012 4:05 pm
Location: Portland, OR

Re: how to mix graphite powder to get shielding paint

Postby Gregory nangle » Tue Apr 12, 2016 2:12 pm

David Schwab wrote:
Gregory nangle wrote:the best thing to do as a graphite expert is to use a mixture of isopropyl alcohol and graphite powder (be sure the powder is truly powder) spray this on and then follow that after it dries with a coat of shellac thinned a bit with denatured,they both use the same airborne finish to dry.must be sprayed! the first coat or two of your mixture will pull off the surface until its sealed in with the shellac.


Wouldn't the shellac act as an insulator? How are you going to make an electrical connection with the paint?

Personally I never found the carbon based paints to work very well, and in most cases there's very little reason to shield control cavities, which is what it's mostly used for.


i use it for electroplating so i cant really speak to its ability to shield. usually we glue down a copper wire to the edge of the paint and then bring paint over that to the bare copper and it conducts enough to plate. for shielding i woudlnt think this is an especially great way to achieve a good shield either but if i had to venture a guess baout what the origianl poster was trying to do that was it. the shellac does not conduct but the particles of graphite suspended(at a great density of course) in it are touching in enough places to conduct. id just use foil and call it day too though! :)
Gregory nangle
 
Posts: 35
Joined: Fri Jul 31, 2015 12:07 pm

Re: how to mix graphite powder to get shielding paint

Postby David King » Wed Apr 13, 2016 2:18 pm

You don't need a high conductivity for shielding at low frequencies. You do need a solid connection to ground which is usually the more challenging part of the problem. Here's a bit of info on RF shielding that might be useful:
http://www.thermospray.com/faqs/EMIRFI.html
David King
 
Posts: 2428
Joined: Sat Jan 07, 2012 10:01 pm
Location: Portland, OR


Return to Electronics

Who is online

Users browsing this forum: No registered users and 2 guests

Your purchase from these sites helps support the MIMForum, but only if you start at the links below!!!
Amazon music     Amazon books     Amazon tools     Rockler tools     Office Depot    

The MIMF is a member-supported forum, please consider supporting us with a donation, thanks!
 • Book store • Tool store • Links •