This is used is something glass people do. It can also be used to
support hollow PMC objects in the kiln; however, it is carcinogenic,
and most PMC users have switched to vermiculite.
(Please don’t post saying some vermiculite may contain asbestos, I
know, I know, this topic has been done to death on every PMC list.)
I wouldn’t use the alumina hydrate myself.
Chicago area, Illinois, USA
Metalsmith, Certified PMC Instructor
Studio 925; established 1992