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