Brush on shielding paint in small quantities?

rwkeating

rwkeating

Oct 1, 2014
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#1
The main shielding paint that has been talked about here is the spray on variety of MG Chemicals Super Shield Nickel 841AR. The brush on versions of that only comes in larger quantities that are expensive and in sizes larger than I could ever use..

Since I build so few instrument (and over long periods of time,) I feel an aerosol solution probably wouldn't last and therefore would be a waste of money. Is there a brush on shielding paint that is in the ballpark of the Super Shield Nickel and that comes in a small size?
 
#2
What's the smallest "larger quantity" for the brush-on versions? Maybe we could arrange a group buy and split? You're not the only one interested. ;)
 
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#3
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#4
rwkeating said:
Looking at Amazon.com https://www.amazon.com/MG-Chemicals-Nickel-Conductive-Coating/dp/B06XXFRJ5B I see 250 grams (about 9 oz.) for $70.83, Not worth a group buy, but I'd could go for a size half of that.

Now that I compare, the spray https://www.amazon.com/MG-Chemicals...rosol/dp/B01N3AWGNX/145-0733813-6609053?psc=1 is $36.95 for 12 oz. Maybe that's as good as it gets. I just can't help think of the over spray waste and the possibility of the can going bad as it sits around between builds.
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Hey RW;

I've been using MG Chemicals Nickel Shielding Paint for about 15 years; maybe 60 basses. I'm very happy with it. Fast to apply, nearly foolproof, should be good for many decades.

MG makes a lot of different shielding paints, for different applications. The one I use is 841AR Super Shield. Here's their own web page on it:

841AR – Super Shield Nickel Conductive Coating

They sell it in a little 5 ml liquid bottle, for around $15. I didn't see the little bottles listed on Amazon right now. Check electronics suppliers. The 5 ml bottle will shield 2-3 basses, brushing it in. You don't need to slobber it on, just two light coats.

It's better to apply shielding paint over a painted/sealed surface, rather than bare wood. On your bass bodies, you should paint/finish the control and pickup cavities along with the outside of the body. Put the shielding paint in after the body is finished.

I used the spray cans for about 12 years. I went through maybe 8 cans to do 50 basses. The spray cans are about $40 each these days, but they are simple and fast to use. There isn't really much overspray waste. They use a small pattern nozzle. I makes like a 2" circle at 6" distance, not a wide oval fan like most spray paints. You do need to clean the nozzle after each use. Spray it upside down for 3 seconds, then wipe off the tip. If you clean the nozzle each time, the can will last in the cabinet for a couple of years at least. I did have one leak down on me, and thoroughly shielded one of my cabinets!

The spray can is a good investment if you forsee shielding up to 7 basses in the next 4 years.

These days I apply it with a spray gun, which is even more efficient. I bought one of the 150 ml cans for about $55 on Amazon (three years ago?). It'll probably do 40-50 basses. I spray it through one of the cheap little HVLP touch-up guns. That gun is used only for the shielding paint. I run it at about 20 psi, fan control off. It sprays about a 1" circle at 4" distance. Hardly any overspray and waste.

The procedure:

On my production instruments, I use mask plates made from 1/4" plywood or 1/8" masonite which pin right onto the body.

IMG_2122B.jpg


I open the can of Super Shield and stir it thoroughly. You must do that every time. I use a small ladle to put about three tablespoons of the paint into the gun's cup. Check the spray from the gun, 20 psi, fan closed.

I spray one full coat in the cavity, rotating it around as I go to make sure I get all the side walls. Let that dry 10 minutes, spray a second coat.

Dump any remaining paint from the cup right back into the can. Run some DNA through the gun to clean out the nozzle. Seal up the can and put it back on the shelf. That's it.

I lift the masking plate off the body, any time. Super Shield, sprayed, seems to be fully cured in 30 minutes.
It's nice and neat, a dull silver-grey color.

IMG_7063B.jpg


On one-off instruments, I use masking tape and Kraft paper.
 
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#5
Bruce Johnson said:
It's better to apply shielding paint over a painted/sealed surface, rather than bare wood. On your bass bodies, you should paint/finish the control and pickup cavities along with the outside of the body. Put the shielding paint in after the body is finished.
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That's interesting, what's your reason for this Bruce?
I've seen other folk saying that the shielding paint can go a bit dusty or crumbly and that it is better to have a top coat of something over the top of it.
 
#6
Flying B said:
That's interesting, what's your reason for this Bruce?
I've seen other folk saying that the shielding paint can go a bit dusty or crumbly and that it is better to have a top coat of something over the top of it.
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I'm not sure what the base paint of Super Shield is, but it's something like Krylon. It has a light solvent smell, but not nasty. MG's own tech sheet says it's made to stick well to plastic enclosures. It'll bond very well to a fairly smooth layer of polyester, polyurethane, nitro lacquer, etc. If you apply it on bare wood, it will sink in some, making an uneven coating. Super Shield isn't intended to be used as a grain filler. It's supposed to be applied pretty thin, like 4-6 mils. Slobbering it on real thick doesn't make better shielding. For reference, copper shielding tape is only 1 mil thick.

Also, it's good general practice to paint the inside of all your cavities to seal them up against moisture. Do that first, then spray the Super Shield over it.

The complaints about dusty crumbly shielding paint are almost all with the black carbon-base shielding paint. That stuff is horrible. I gave up on it back in the '90's. The problem with it is, if you don't stir it up thoroughly, and you smear it on like some kind of wood filler, when it dries it'll shed carbon dust. Conductive carbon dust floating all around the cavity, shorting things out. It's incorrect application, but so many people do it, and it turns them off to shielding paint. I wish Stew-Mac and other guitar parts suppliers would stop selling it.

That carbon-base shielding paint is also made by MG Chemicals. It's a lower priced shielding paint made to be robot-sprayed into electronics enclosures in mass production. Controlling the spray mix and coating thickness, it works fine. It's a little higher resistance than the Nickel paint, but still acceptable for our use. The problem is selling it to Luthiers in liquid form, who slop it in there way too thick.

The Nickel paint doesn't seem to have that shedding problem. The nickel particles don't really come up to the surface of the paint as it dries. If you rub dried Super Shield Nickel with your finger, nothing really comes off.
 
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#7
I bought some off-brand jet black "shielding paint", naively thinking it was the same stuff as MG, nope. Worthless stuff, took me three heavy coats to get any continuity from point to point. Junk. Ive bought the little pots of MG before, but I only got two basses out of it. It tends to dry up in the pot, even with the cap tightly closed, but ive read you can "reactivate" it using a little acetone.
 
#9
rwkeating said:
The main shielding paint that has been talked about here is the spray on variety of MG Chemicals Super Shield Nickel 841AR. The brush on versions of that only comes in larger quantities that are expensive and in sizes larger than I could ever use..

Since I build so few instrument (and over long periods of time,) I feel an aerosol solution probably wouldn't last and therefore would be a waste of money. Is there a brush on shielding paint that is in the ballpark of the Super Shield Nickel and that comes in a small size?
Click to expand...
I use the small 12 ml bottles (will do a couple of instruments) of MG Super Shield, it's water-based, brush on, and readily available on Amazon:

MG 841-WB Super Shield On Amazon

MG 841-WB in use...
 
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