Crude coil sheilding paint

[ron_o]

Just a thought!

Has anyone tried Aluminized or Crome Paint?

Hi homefire,

Aluminium and Chrome based paint use metallic flakes which are normally coated with a chemical that prevents the carrier resin blackening the flakes. This coating acts as an insulator and prevents electrical conductivity between the metallic flakes , so i doubt that they would work in this application.

Regards ron

[mts]

How do you attach a ground wire to shielding that is made out of paint? I'm assuming that a ground wire is still required in order for the shielding to work its magic.

[Kev]

Don't use this paint!

Hi,
I'm very sorry, this preparation is way too corrosive, it has over time turned my ground wire connection to oxide powder.

The carbon needs to be extracted from the manganese dioxide and other chemicals and washed carefully before adding to the paint....maybe better to use graphite powder instead, if you can get it, or just use the powdered carbon anodes from the battery.

{Washing egg from face}
Kev.

[ApBerg]

Hi,
I'm very sorry, this preparation is way too corrosive, it has over time turned my ground wire connection to oxide powder.

The carbon needs to be extracted from the manganese dioxide and other chemicals and washed carefully before adding to the paint....maybe better to use graphite powder instead, if you can get it, or just use the powdered carbon anodes from the battery.

{Washing egg from face}
Kev.

Hi Kev,

Thanks for warning !

... searsing on Ebay I found this.. is powder and must be mixed with water.
Made some small tests, must say I like it. Is easy to paint and tools can be cleaned with water . I sticks 'good' on ABS plastic.. if you keep in mind that it is on waterbase !!
The multi meter like's it also, dry is it some 500 Ohms / 10 cm, think this is dependend on the thicknes from the paint layer .

Best regards.

Ap

http://www.ebay.de/itm/Kreidezeit-Ab...item415485c6f8

http://www.ebay.de/itm/Kreidezeit-Ab...item3a6d689054

[simonbaker]

Hi,
I'm very sorry, this preparation is way too corrosive, it has over time turned my ground wire connection to oxide powder.

The carbon needs to be extracted from the manganese dioxide and other chemicals and washed carefully before adding to the paint....maybe better to use graphite powder instead, if you can get it, or just use the powdered carbon anodes from the battery.

{Washing egg from face}
Kev.

Egg white can be a good glue base -- save it!

Thanks for follow-up -- no problem, all in a day's tinkering. Worth the experiment to find out the facts.

Now -- you can still use your idea if you take some of that gold you find and make a non-corrodable shield wire out of gold ...

[Kev]

Egg white can be a good glue base -- save it!..

had to re-read my post before it sank in!

Thanks AP I'll look into that product.

I've just used two 'CATHODE' (wrongly called them anode above) carbon rods ground to powder with a dremel and mixed with a little plastikote paint. It worked out well, giving about 2kOhm per inch, but my 4500 doesn't like it, and refuses to ground balance.

A graphite paper shield from an original Minelab coil measures about 45 - 100 Ohms all over, so I think I need to get the resistance way down below what I have.

Cheers Guys.
Kev.

[turtlebowl]

Great thread! I have read all the posts in this thread but to busy/lazy to search the forum relating to this great topic.
Has anyone tryed pulverising pencil lead for graphite? I did some quick tests this morning after reading this thread.
Different pencil manufacturers lead produce different readings. Relative to lead diameter I think. Perhaps composition as well? I tryed three different manufacturers.
Anyways I am curious to know this. Using the same compound will a 1/16" round straight pencil lead have the same resistance as a broad solidly filled in circle? I ask this becuase my measurements this morning were simple test leads on opposing ends of the pencil lead.
Resistance was only about 10 ohms per inch. Then it occured to me that maybe if the graphite field (as in sprayed on) were broader and much thinner the resistance would be higher? Would seem so.
So has this idea already been disscussed elsewhere?
Phil

[golfnut]

you could use a foil quiche tray

[Kev]

Hi turtlebowl,
Yep, graphite powder has been used by some, and Minelab had traditionally used this on cardboard for shields, it's like a thick coating of pencil lead, and measures about 45 to 100 ohms. I imagine a thicker lead will have less resistance.

I've just put the forth ground carbon rod into my small pottle of paint (50 mils) but I'm still only getting 200 Ohms, I need to get it down to 100 Max for my GPX. A coil for a non-fussy PI such as a Hammerhead, would be happy with a shield of 1 or 2k Ohms.

PLEASE NOTE: I got big sparks from my Dremel last night while grinding down carbon battery rods. Some of the dust must've been sucked in and built up around the mains input. Please be careful if you do this. I am now going to insert the Dremel head into a container and grind the rod inside of it so that the carbon dust will not be floating around everywhere.

Be Safe
Kev.

[simonbaker]

Great thread! I have read all the posts in this thread but to busy/lazy to search the forum relating to this great topic.
Has anyone tryed pulverising pencil lead for graphite? I did some quick tests this morning after reading this thread.
Different pencil manufacturers lead produce different readings. Relative to lead diameter I think. Perhaps composition as well? I tryed three different manufacturers.
Anyways I am curious to know this. Using the same compound will a 1/16" round straight pencil lead have the same resistance as a broad solidly filled in circle? I ask this becuase my measurements this morning were simple test leads on opposing ends of the pencil lead.
Resistance was only about 10 ohms per inch. Then it occured to me that maybe if the graphite field (as in sprayed on) were broader and much thinner the resistance would be higher? Would seem so.
So has this idea already been disscussed elsewhere?
Phil

I once tried rubbing a soft pencil on rough paper to make as thick a layer as I could, then measured resistance. I don't remember actual resistance, but I believe it was something like 1K per inch maybe. That would still discharge static electricity probably -- whether that would be useful depends on how shields are supposed to work.

Since then I acquired a bottle of graphite as well as a spray can, but have yet to test it out. It's probably not simple to prove a shield is good -- you need to find a situation where it is needed (wet grass? certain soil? certain noise environment?) and compare to another shield.


-SB

[moodz]

.... you could just type this number into ebay 130474942236

$7 for 350 gram of chemically pure graphite powder.

[turtlebowl]

yet another concoction

Here is a great idea from our luthier friends. Produces a paintable approx 100 OHM shield. The link in the article has several other formulia.
DIY Conductive Paint for Cavity Shielding
http://www.talkbass.com/forum/f38/di...elding-589012/

The formula I used was one part 3M Scotchkote Liquid Tape, 1.5 parts graphite powder, and 1 part Acetone. I created the mixture in small batches, just enough for one coat since the solution starts to setup in about 10 minutes. The solution was painted on in three coats using disposable acid brushes allowing 20 minutes between applications.
Note that the spacing on that Precision Bass is approx 6 inches and 3 coats. Wonder what 1 coat and 1 inch would be?
Phil

[simonbaker]

Here is a great idea from our luthier friends. Produces a paintable approx 100 OHM shield. The link in the article has several other formulia.
DIY Conductive Paint for Cavity Shielding
http://www.talkbass.com/forum/f38/di...elding-589012/

The formula I used was one part 3M Scotchkote Liquid Tape, 1.5 parts graphite powder, and 1 part Acetone. I created the mixture in small batches, just enough for one coat since the solution starts to setup in about 10 minutes. The solution was painted on in three coats using disposable acid brushes allowing 20 minutes between applications.
Note that the spacing on that Precision Bass is approx 6 inches and 3 coats. Wonder what 1 coat and 1 inch would be?
Phil

Looks promising. I couldn't find anything called exactly "3M Scotchkote Liquid Tape", is there another name? Also, it would be good to find the cheapest binder possible.

-SB

[Vortxrex]

Can't we use any good quality paint (that will stick to the coil shell or coil covering) and add the same ratio of graphite powder?

[maikl]

Cheapest possible binder in # 161 http://www.geotech1.com/forums/showt...t=17396&page=7