Crude coil sheilding paint

[Davor]

160ohm seem lowish already

[Kev]

Looks good, thanks for the link!

-SB

It seems good Simon, 160 Ohms across coil from 2 thin coats, I can hardly tell I've used any from the tin.
I may give it one more coat and see if my Minelab spits it back at me.
Appears to be more carbon in it than I'd like, but all the same it's very similar to what Coiltek use.
Will report back as to how it performs in the field.

Cheers
Kev.

[simonbaker]

thanks

Hi,
I've ordered some of this to try, they ship internationally

https://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Shielding/Conductive_Shielding_Paint.html?actn=100101&xst=3&xsr=515

It's composed of predominately graphite with a little carbon black.
I believe the pure carbon black paints are not the best for Minelab PI.

Cheers
Kev.

Looks good, thanks for the link!

-SB

[Kev]

Hi,
I've ordered some of this to try, they ship internationally

https://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Shielding/Conductive_Shielding_Paint.html?actn=100101&xst=3&xsr=515

It's composed of predominately graphite with a little carbon black.
I believe the pure carbon black paints are not the best for Minelab PI.

Cheers
Kev.

[Davor]

Interesting.
I occasionally visit some agricultural shops to buy stuff such as enological steam-activated charcoal - which is a few classes purer and better than the medicinal charcoal (yuck!). Also a washing soda. I'll pay more attention to graphite now.

[BillNEWAST]

GRAPHITE POWDER SEED-FLOW LUBRICANT
Manufacturer Name: VAN SICKLE PAINT
MFG.UPC: 82095995003
Ensures proper lubrication & reduces friction
Use in high-speed planters & farm equipment
Helps seed flow smoothly &...

http://www.greatplainshardware.com/products/9950-0-5-powder-graphite.html

I haven't tested this stuff for conductivity, BUT it's Pure Graphite as per the makers MSDS Sheet.
Sincerely
Bill Adams

[WM6]

Good remark, thanks Dave.

[satdaveuk]

Hi WM6
The Synthetic Graphite that I use is made by Graphite Trading company UK.
Interesting thing to check if using Graphite spray check contents before buying because best you going to get is natural graphite mixed with alcohol which is 85% carbon but quite often its abstracts from coal which is not true Graphite, so thats one to watch out for because although conductive its not designed for what we use it for due to low conductivity and build .
If your mixing into Epoxy resin they advise manufactures to only use Synthetic Graphite due to its molecule build and conductivity.
All the best

[multieagle]

Carbon papers are wax based, so don't expect much.

Thank you. I'm going to move on to 6v heavy duty batteries. Will try using both the chemical compound and the carbon rods. See my previous post.

[multieagle]

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.

You can easily remove the manganese dioxide from the other powders: http://www.youtube.com/watch?v=BVXm1O3MtqY Perhaps that would render the battery chemicals useful?

[Henrikras]

Maybee some stupid Questions. But why not mix the powder in to the plastic before you cast the Shell. then the Shell got the Sheilding.?? If you can spray/paint inside a shell, you properly allso can spray/paint outside the Shell, so why not between ??
Will it work If I sprayed the Sheilding outside a search coil, which didn't got enough spray inside before I closed it ? If I can connect to the wire.
Henrik

[Davor]

Somewhere I recall reading that carbon paper, the kind used by artists to transfer drawings, images to art paper, could be used as shield material.

Carbon papers are wax based, so don't expect much.

[satdaveuk]

Thanks for your experience.

I am usually spraying graphite direct to finished coil(s) and not to coil housing, but to lower parasitic capacitance your approach would be better.

Hi
Graphite in a spray can is great the only problem is the price and I presume the carbon content within that graphite will vary according manufactures so some brands of spray you maybe using half a can or so before you get the conductivity you require.
As promised I will pop in the workshop later and tell you the make of graphite I am using because that also may well vary from brand to brand and maybe thats part of why we have had good and not so good results on here.
What may interest you is the synthetic graphite I use comes from the off cuts when they are making brushes for motors etc. they collect them up and with precision grind it all up to a powder thats finer than talc powder, thats why its better to wear gloves because it gets easily into the paws of your skin, anyway maybe you can understand its high conductivity due to what it originally came from, all interesting stuff isn't it .
1kg cost around £25, when shielding two coils your using about 3 teaspoonful's and throwing nearly half away so that container of graphite will last years if you think about it, its costing penny's per coil if that.
Regards

[WM6]

Thanks for your experience.

I am usually spraying graphite direct to finished coil(s) and not to coil housing, but to lower parasitic capacitance your approach would be better.

[satdaveuk]

You mean as electrostatic shielding - mixed with graphite? Which brand/product did you use?

All you got to do when shielding styrene project boxes is sand the gloss off the styrene then stick copper type tape to the 4 corners and anywhere else after thats convenient where you want to solder your earth points not forgetting the lid which I always use a permanent soldered wire between the two, then get your Synthetic Graphite which is normally 99.98% carbon and mix with yacht varnish about 1:1 although not critical just make it so it brushes on nicely leaving a little copper showing where you intend to do terminations.
If you want less or more resistant just another coat when dry or lightly sand its as simple as that and sticks like pooh to a blanket.
When in the workshop next will get the manufacture for you, it really works well .
If you look on this forum a while ago I did a whole tutorial on using the graphite which started when first doing experiments right through to total constant success, done and dusted in my opinion for DIY shielding.
When doing coils if directly painting which most of the time I do just put plenty of layers of rubber tape on first to reduce internal capacitance then hospital type paper tape on top which is very adhesive and absorbent then copper tape at each end leaving 5mm or less gap between the two then same procedure as above.
Once this stuff is dry you can hit it with a hammer and it wont fracture yet on the other hand you can still bend your coils lightly when nulling and they easily sand if increasing resistance is required.
The actual bond between the copper and the graphite is good just remember as with the styrene you need to sand the surfaces before applying the mix otherwise it will not bond correctly.
When testing the Graphite for continuity at various points its paramount you lightly sand it first because the varnish comes to the surface which acts as a insulation so you will get false readings.
Another plus side is it actually looks nice very close to gun metal Gray.
Give it a try but don't deviate from what I said because lost count of different chemicals I used based around Synthetic Graphite, also talked for a considerable time with the manufactures who are based here in the uk for advise before experiments began.
Regards