Here's a previously modified pickup I bought used ages ago. It never worked, so I just kept it in a box somewhere. I took it apart today (and took all the polepieces out) to try and get a feel for things before I dismantle my working pickups, and lo and behold, it's full of what very much appears to be caulk. Y'all ever seen or used anything like this before?
Objectively, any soft and/or drying material can be used to pot pickups as long as its dielectric constant doesn't make it too capacitive and as long as it doesn't corrode the components. See epoxied Bill Lawrence's or Gibson Tar Back among others.
My ol' friend luthier-winder did order once some pickups based on his instructions to an Asian maker of OEM parts: those who made the prototypes decided (without notice) to put silicone plumber tape around the screw poles + some thin cushions of foam between magnets and baseplates... It's not that rare either to find silicone used as a way to dampen microphonic covers or rubber elastics around the screws of a DynaSonic in order to avoid squeal.
This "caulked" DiMarzio is certainly ugly as hell but it's not necessarily because of "caulk" that it doesn't work. EDIT - And honestly, I've already found a disgusting wiring mess in stock 4-conductors wired DiMarzio's once I had got rid of their (stock) wax potting...
I've heard of people using a dab of silicone caulk under humbucker covers to damp vibrations.
But I never saw anything like that. And I hope never to again.
Must've been for a guitar that was grouted for humbuckers.
