Benzine is correct. Vitrified pots would probably crack, and even if they did not, the horse hair would not make the distinctive smokey trace.
As I mentioned before, I have reheated bisque fired pots with a propane torch and then placed horse hair on the heated surface and it worked. You have to heat the surfaces slowly and bring them up to a high enough temperature to carbonize the hair. Hold the hair in both hands and loosely drape it over the hot surface.It takes some practice, but I have done lots of them this way.
- Mark (Marko) Madrazo likes this