I don’t know about metal, but as almost anyone who has handled LPs knows, they are prone to static charges. Thus, the use of additives, such as carbon black, which served several purposes, one of which was to make the record more conductive, to lessen the potential charge. ( I know that sounds counter-intuitive, but I can pull some old AES papers I read a few years ago about the subject).
This was a factor in Classic Records’ choice to go for their Clarity vinyl toward the end of their business life; the theory being, the conductive aspects of the vinyl led to all sorts of sonic anomalies.(I do have a few of those records, including a promo set of Aqualung that was released in both conventional (carbon) black and Clarity (translucent) to demonstrate the sonic differences. (My take was that the difference was relatively minor- the far bigger issue for Classic, as most of you know, was QC, non-fill and stitching when he went to the 200 gram flat profile).
As to demagnetizing records, I experimented with it using Lloyd Walker’s handheld bar- I forget the product name. In the same way you could hear very slight differences with some things, it was possible I was hearing an improvement. I quit using for two reasons- I’m lazy, and I also didn’t like the idea of getting a magnetic field anywhere near my phono cartridge.
