RF shielding foil thickness on Pickguards

[StratsRdivine]

I recently learned that the foil on the back of most pickguards are there to shield unwanted interference / RF from sources that might create feedback, etc.  I was curious what thickness is enough to do the job of shielding.  I notice that the shielding foil is obviously over the control knobs, switch etc, not needed anywhere else.  

So for those that may have used mirror acrylic as a pickguard (not polished or chromed metal) does the ultra thin metal deposition of the aluminum coating in the mirror backing provide adequate shielding, or would the application of thicker aluminum foil be needed to block RF?  The thickness difference between foil and aluminum metal deposition on mirror backing is like the difference between plywood and paper, relatively.   I imagine that the foil is at least 20 microns, while the metal deposition mirror backing is less than one micron - but is it enough to block RF?

I suppose another question, would be this - do homemade pickguards without foil shielding (like some exotic wood PG's that I have seen) sound ok anyway in a guitar?  Or do all folks that make pickguards apply foil to the backs?      

[curtisa]

4 hours ago, StratsRdivine said:

I was curious what thickness is enough to do the job of shielding.  I notice that the shielding foil is obviously over the control knobs, switch etc, not needed anywhere else.

I assume you're talking about Strat's and similar, where the rear of the pickguard is shielded but the cavity usually isn't.

Thicker shielding offers better noise immunity than thinner, but has the obvious trade-offs of being more bulky, harder to machine and heavier. Copper foil, aluminium foils and tapes and shielding paints offer a good compromise

 

4 hours ago, StratsRdivine said:

So for those that may have used mirror acrylic as a pickguard (not polished or chromed metal) does the ultra thin metal deposition of the aluminum coating in the mirror backing provide adequate shielding, or would the application of thicker aluminum foil be needed to block RF?

It may provide some shielding, but I personally wouldn't rely on it solely as a substitute for dedicated shielding. The metallic coating is provided for looks, not for shielding, and there's no guarantee that the metallic coating is uniform or in good contact with ground at any point.

 

4 hours ago, StratsRdivine said:

I suppose another question, would be this - do homemade pickguards without foil shielding (like some exotic wood PG's that I have seen) sound ok anyway in a guitar?  Or do all folks that make pickguards apply foil to the backs?      

Non-conductive pickguards should be shielded to the same degree that the original pickguard was in order to expect the same performance. You could avoid the shielding if you choose, but the risk is that it will be more prone to picking up all sorts of electrical garbage than it was with the stock pickguard fitted. It's also possible that if the original wiring was taking advantage of the pickguard's foil to maintain ground connections to various parts of the guitar, the guitar may not work properly if fitted with an unshielded pickguard.

[StratsRdivine]

Thanks a ton man!  Very thorough answers.  I was also wondering about grounding as well, as the control knobs and switch are connected via the foil.  So that pretty much answers my question.  Gotta apply the foil.  

[Norris]

The thickness of the shielding material is more to do with robustness & ease of handling than anything else. AFAIK one molecule thick is enough to shield, but would be impossible to handle.

As Curtisa says, it's all got to be connected to ground to be effective - you are essentially making a Faraday cage