On 15/12/15 20:48, Terry Coombs wrote:
Jon Elson wrote:
Terry Coombs wrote:


I don't have a pottery supply near , but I do have a large pile of
fiberglass batts . You think they'll work at the temps you use ? The
grates aren't so awkward in shape , I plan to build an enclosure with
firebricks and preheat with my foundry burner . Heat 'em both up and
let one soak while I weld on the other , swap as they cool .

No, you can melt fiberglass on a kitchen stove. I don't know what
the glass type is, but really low melting point.

Jon
THanks , looks like I'll be inventorying the fire bricks . I've got enough ,
just gotta dig 'em out of storage .

The fact it can be melted in a kitchen stove flame isn't really a good
indication of its service temperature as it was exposed to the naked
flame, it may well be fine to insulate your piece if placed on it after
heating rather than exposing it to direct flame, you may just get some
binder burning off. I don't know about fibreglass insulation but some
refractory fibre material I use on occasions use starch as a binder, a
bit whiffy when burning out but fairly harmless. I work with glass as an
amateur glass blower and normal annealing temperature for soda lime
glass is around 500C and fibreglass insulation is made from a mix of new
and recycled soda lime glass. This table may give you some idea
http://www.engineeringtoolbox.com/in...res-d_922.html .
Regarding melting fibreglass on a kitchen stove I've melted or badly
damaged woven silica cloth with a propane torch and that has a far
higher melting point than glass, concentrated heat on fine fibres does
the damage.