It is a special kind of chemical treatment if I remember correctly but it is not very common with pearls, I think! If recalling rightly, it is a rather expensive way of enhancing luster but it is done with gem stones I believe. There should be a post somewhere here on the forum.
https://www.pearl-guide.com/forum/pearl-books-resources/3344-afterthoughts-ze.html
It was one of Zeide's claims about mass-market pearls (PPB = pearl-plated bead = thin-nacre akoya). Total crap, just like everything else she said. Being a young spat, Mary, you weren't around for that. With all the recent (undeserved) attention Z's been getting, I thought I'd make a little joke about it.
https://www.pearl-guide.com/forum/pearl-books-resources/3344-afterthoughts-ze.html
It was one of Zeide's claims about mass-market pearls (PPB = pearl-plated bead = thin-nacre akoya). Total crap, just like everything else she said. Being a young spat, Mary, you weren't around for that. With all the recent (undeserved) attention Z's been getting, I thought I'd make a little joke about it.