My BIL is currently doing pottery with horsehair for glazing.

Low temp firings, AFAIK, and thus not good for table pottery, but if you want to immortalize your steed (or kitty, or whatever). And you wouldn't want to subject such an heirloom to everyday abuse anyway.

See for examples.

He only does his gas firings during the day; he's afraid the neighbours would call the FD if they saw the flames shooting out of a box outside his house at night....

Cheers,