The horse hair vessels' surface decoration are indeed made with hair from horses. The hair is laid upon glowing hot pots straight from the kiln, they sear onto the pot's surface and will leave carbon markings.

The raku vessels have copper in the glaze, hence the metallic iridescent look. The pots are removed from the kiln at bright red heat and placed in containers with combustible materials. 

The raku and horsehair pots are not food safe.