Hi Harry an LML

Ceramics are very fire resistant however they aren't the whole story.  If the
heat flux on one side of the ceramic is 2000 degrees, the temperature on the
back of the ceramic is 1995 degrees and can ignite what is on the back.  This
is due to the relatively small insulating value.  They are also very heavy
for their structure.  There are many ceramics but the specific gravity range
is from around 3.2-3.3 but are as low as 2.7 and as high as 5.7.  Glass is
much lighter at 2.58 for E glass and 2.48 for S glass.  Carbon varies a bit
also but is generally around 1.9, Kevlar at 1.41 and Spectra at .96.

For fire barriers, blankets made of ceramics with other fire resistant
materials can be pretty incredible.  Our company is working with the FAA and
the US Navy on fire hardening for airliners and ships and have a patent on a
carbonized fabric that when used either alone or with ceramic fabric such as
Nextel, can withstand a LOT of heat for a very long time.

Dan Newland