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Conductive Paint

11/5/1997 11:09 AM
David Axt
Conductive Paint
Does conductive paint work well for shielding inside of a guitar?  
If "YES" where can I get some and is it very expensive?  
If "NO" how can I install shielding to reduce hum? Can I use aluminum foil and glue?  
11/5/1997 2:06 PM
J Epstein

Stewart-MacDonald, pretty epensive.  
Copper foil is better, Stew-Mac sells it with stuckum already on it.  
Stewart-MacDonald : 800 848 2273  
(maybe a web page somewhere too)
11/9/1997 3:20 AM
Steve Ahola

Stewart-Mac stock #29  
Conductive shielding paint/8 oz $26.44  
(Is this the water-based carbon paint that dries with a black finish? I had a bad experience with the older style MEK-based paint that bled through the masking tape and mottled the finish on my LP Standard around the pots! The carbon paint is a lot safer to use around nice guitar finishes.)  
Their web site:  
Steve Ahola
5/9/1998 11:41 PM
don schultz

I bought a can of this from SM in the last 6 months. It is water based and does not bleed through masking tape. I found it to be "dirty" to touch even after drying. I've done 2 guitars with it with excellent results.
5/11/1998 12:21 AM
Steve A.

    I'm sure that they took the MEK-based paint off the market (these days its considered to be a hazardous substance).  
    The water-based carbon paint is "dirty", almost like charcoal. I suppose that once you've added the ground connections you could coat it with a clear coat of something.  
    After doing 2 guitars, how much of the can is left? (I did one strat with copper foil and it took many hours- its a lot less of a hassle to just paint the cavity.)  
    Did you prepare the cavity at all before painting it? I think something like TSP might take the sheen off just fine and allow the carbon paint to adhere better (I remember it beading up when I used it before so it took maybe 3 coats before the entire cavity was covered).  
Steve Ahola
5/11/1998 6:02 PM
don schultz

I am sure you are right about the MEK version.  
I still have over 1/2 a can left. I gave each guitar 2+ coats. I hate cleaning brushes, so I use the cheap foam type. As far as taking the shine off surfaces, there are chemicals made for the purpose in the paint section of any home improvement store, but I used a little sand paper, and cleaned the dust out well.
11/10/1997 4:09 PM
Austin C

Hi Dave  
Conductive paint is quite effective for shielding but you can do better.  
In 1976 a guy called Henry W. Ott did some experiments into the shielding properties of different metals, and guess what..........  
COPPER SUCKS! and Aluminium sucks even harder. At R/F these two work well, but at audio frequencies they have a field reduction capability of only 2 and 3dB respectively (0.02" thickness).  
Steel on the other hand kills around 10dB, at the same thickness. If you inrease the thickness to 0.125" this figure inreases to around 40dB.  
This makes shielding a guitar somewhat of a challenge. I have never heard of steel foil and to make a steel enclosure into the shape of a control cavity would require extraordinary sheetmetal skills.  
Sorry to complicate the issue but keep this in mind when selecting a shielding paint, maybe there's one which utilises steel instead of copper.  
Another source of hum is in the basic design of guitar electronics. The use of the shielding braid (in a standard guitar lead) as the signal common renders the shield useless (as a shield). A magnetic shield's purpose is to absorb pulsed magnetic waves of flux and provide a low resistance path to earth for these pulses to travel.  
Using the shield braid as the signal common will cause the signal common to 'float'up and down in sympathy with the noise pulses. Logically this leads me to describe the standard method of connection as "Have some noise!"  
This has bugged me for most of the 19 years I have been playing guitar and there are solutions.  
I'll shut up now.  
See ya  
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