6 metres of sumfink

[Bristlehound]

If I remember correctly, the blackboard paint (US: chalkboard?) you can buy is conductive... but I have no idea how conductive it is. I remember (years ago) it giving a positive reading when some chap was using a damp-meter on my parents' house where my little sisters used to have a blackboard - long since wallpapered over.

Just FYI.

 

[Mat UK]

If I remember correctly, the blackboard paint (US: chalkboard?) you can buy is conductive... but I have no idea how conductive it is. I remember (years ago) it giving a positive reading when some chap was using a damp-meter on my parents' house where my little sisters used to have a blackboard - long since wallpapered over.

Just FYI.

Hmm, I would bet that the colour is taken from carbon or some derivative, shielding paint has got that matt to touch blackboard vibe, thinking about it.

 

[Mat UK]

Right, here’s what I’ve done.

3 teaspoons of acrylic paint

7 teaspoons of graphite powder, 1 mixed in at a time

This creates a thick paste

I then add 8 squirts of distilled water to bring back down to a paintable creamier state

Voilà

And I had just enough time this morning to get a coat on

I’m planning on doing about 3 coats, possibly 4.

So to summarise:

- 3 teaspoons of acrylic paint
- 7 teaspoons of graphite powder
- 8 squirts of distilled water

So given that the water will evaporate off I give that a graphite percentage of 70%.

I’ll give it a preliminary test this evening.

 

[Davecam48]

Nice experiment Mat! However I'm of the opinion that any shield especially RF needs to be 100% conductive i.e. zero ohms from any point to any other point on the object, otherwise you run the risk of making isolated mini r.f. re-transmitters within the instrument which could be a whole different problems. My approach to shielding is quality coax cabling with a woven copper shield, as well as keeping the electronics sections small and totally shielded with thin copper sheet with a quality thin double sided tape so as to be able to solder corners and connected lines to other shielded pockets within.

Back in the bad old days of servicing two-way and sonar equipment ( which is on a whole other level of induced noise) this was accepted as going a long way to greatly reducing the problem.

When I was playing guitar 100 years ago I had a Burns Orbit 3 transistorized amp which was a great amp but used to pick up the police radio transmissions from the local Cop-Shop across the road from the hall we used to play in. I did try to shield it with aluminium foil but the results were poor due to the nature of the amp's power supply supply which was some kind of floating earth system. As a side note to this.......one night we got a loud and clear transmission from the amp along the lines of " Car three .....tell the kids at Fallon House to turn down the sound...........the picture theatre manager is complaining again they can't hear the movie!!!!"

DC

 

[Mat UK]

Nice experiment Mat! However I'm of the opinion that any shield especially RF needs to be 100% conductive i.e. zero ohms from any point to any other point on the object, otherwise you run the risk of making isolated mini r.f. re-transmitters within the instrument which could be a whole different problems. My approach to shielding is quality coax cabling with a woven copper shield, as well as keeping the electronics sections small and totally shielded with thin copper sheet with a quality thin double sided tape so as to be able to solder corners and connected lines to other shielded pockets within.

Back in the bad old days of servicing two-way and sonar equipment ( which is on a whole other level of induced noise) this was accepted as going a long way to greatly reducing the problem.

When I was playing guitar 100 years ago I had a Burns Orbit 3 transistorized amp which was a great amp but used to pick up the police radio transmissions from the local Cop-Shop across the road from the hall we used to play in. I did try to shield it with aluminium foil but the results were poor due to the nature of the amp's power supply supply which was some kind of floating earth system. As a side note to this.......one night we got a loud and clear transmission from the amp along the lines of " Car three .....tell the kids at Fallon House to turn down the sound...........the picture theatre manager is complaining again they can't hear the movie!!!!"

DC

Ha, picking up police transmissions sounds like an great way of getting up to mischief - or a good way of alerting local criminals to police whereabouts.

Yeh, I understand copper is better... but I just prefer the look of paint. And I'm thinking if it's good enough for Stewmac to sell it should be good enough to use. I'll stick with my experiment and see how it goes - I may decide to use copper in the future though... it depends how this guitar works out.

 

[LuckyJinx]

Hi Mat, I just saw a video and remembered your conductive paint tests.



Seems it's close to what you ended up with, similar formulation but different binding agent. I guess it depends on how much the binding agent itself reduces in drying.

 

[Mat UK]

Hi Mat, I just saw a video and remembered your conductive paint tests.



Seems it's close to what you ended up with, similar formulation but different binding agent. I guess it depends on how much the binding agent itself reduces in drying.

Great video - he had interesting results. Thanks for posting.

His mix seemed on the thin side to me, my understanding is that to lower the resistance layering up is the trick, which acrylic paint does a treat. When he says the best you’re going to get is 1k-2k Ohm resistance for home made paint that doesn’t tally up with my tests: across the same(ish) distance he was measuring I read about 150-240ohms - but his issue is the thickness of his test application.

Anyway, it’s good to see others are having success with similar approaches, so thanks for sharing!

 

[Mat UK]

In related news, this is the body with the cavities painted up and tabbed for control plate contact. I’m pleased with the results, continuity measurements match up with my tests too

Slowly, slowly catchy monkey

 

[R. Stratenstein]

Interesting experiments, Mat. You might also try to locate fine carbon black powder, to compare against the graphite.

But did I miss the discussion where Leo used copper cut out to match the cavity shapes, and held the pieces in place with what looks to me like glazier’s points, pushed into the sides of the cavities and soldered to the copper pieces? Paint looks much friendlier a process.

 

[Mat UK]

Interesting experiments, Mat. You might also try to locate fine carbon black powder, to compare against the graphite.

But did I miss the discussion where Leo used copper cut out to match the cavity shapes, and held the pieces in place with what looks to me like glazier’s points, pushed into the sides of the cavities and soldered to the copper pieces? Paint looks much friendlier a process.

Look what the cat dragged in! Do you now qualify as some kind of guardian angel, only appearing in ones most dire moment of need... you’re like Dolly Parton in that film that I can’t remember the title of...

Anyway, you didn’t miss the discussion, I decided against the copper sheet method on the grounds that I prefer the look of the paint approach - I have no doubt in the superior functional qualities of copper, but alas, I just felt it was too fussy for me... unlike trying to make a conductive paint from scratch, no, that’s not fussy at all!

Hope you’re well Rick? There is an R.Strat shaped hole in the DIY forum these days...

 

[R. Stratenstein]

Look what the cat dragged in! Do you now qualify as some kind of guardian angel, only appearing in ones most dire moment of need... you’re like Dolly Parton in that film that I can’t remember the title of...

Anyway, you didn’t miss the discussion, I decided against the copper sheet method on the grounds that I prefer the look of the paint approach - I have no doubt in the superior functional qualities of copper, but alas, I just felt it was too fussy for me... unlike trying to make a conductive paint from scratch, no, that’s not fussy at all!

Hope you’re well Rick? There is an R.Strat shaped hole in the DIY forum these days...

Hey, Mat. Thanks for the kind words. I'm doing well, thank you, even "weller" since Friday, which was my last day ever--at work, that is! I am now an officially retired old coot/fogie/fossil/fart, et. al. So I can fly in more often on my gossamer wings, with my giant twin, um, faeirie wings to dispense questionable knowledge and advice (would that be advise over there?) to the great unwashed. I am still in the throes of catching up several on much deferred home maintenance projects, but I'm afraid you may be seeing a bit more of me around here in coming days. . .

 

[I_build_my_own]

Congrats Rick to your Retirement!!!

 

[MM73]

Love these threads.

While figuring exactly how much distilled water is in 8 squirts, I had a chuckle over the comparison of Rick to a guardian Dolly Parton.



...and now Rick is retired!
Congrats!!!

Fine looking guitar by the way Matt. What’s next?

 

[R. Stratenstein]

I’ve had to give up the spike heels, but never the rhinestone dresses nor beehive hairdo!

 

[R. Stratenstein]

And thanks to those who congratulated me: so far, so good!