@bb1c524f I think my three key reuse questions are: is this for food contact? Is it for skin contact? Is the diy technique accelerating any chemical reactions? 
Like, heavy metal enamels are a horrible policy choice, but they don’t hurt consumers if you’re just drinking the contents of the bottle. But if you’re reusing it by submerging it in water for some reason, or you’re melting the glass - then you’re increasing entropy for the paint. Does that make sense?