The whole point of using cotton as dielectric is to loosely cover the wire, so the main dielectric involved with the signal is air. Tight coverings exhibit dielectric absorption (DA), and teflon is the best solid, but not as good as air.
If you treat your cables with something, then that's the dielectric which a signal sees. If the dielectric is not air, you're defeating the purpose of a cloth dielectric.
If you treat your cables with something, then that's the dielectric which a signal sees. If the dielectric is not air, you're defeating the purpose of a cloth dielectric.