For holmz: check this website for cotton-insulated wires: https://www.vhaudio.com/unicrystal-occ-silver-wire.html
BTW: the way I understand it, the electromagnetic field around the conductor arises the moment it gets connected. What we call the 'signal" is actually a disturbance of this field traveling along the conductor at near-light speed. However, the material-dependent impedance of the conductor is responsible for the time-aligned transmission over all frequencies; hence the "smearing" of the signal at higher impedance. This part is still puzzling me: if the event takes place around the conductor and not through it, how can its material make a difference? Or are some aspects of the field dependent on it? But again, I am not an electrical engineer or a physicist.