[Stoves] RE Clay Stoves - Columbia University

[Crispin Pemberton-Pigott]

Dear Friends

Regarding the silica / silicon question Bruce Berger writes:

 [snip]

The material expanding during heating and contracting during
cooling at 573 C is silica or silicon dioxide (not silicon) in its quartz
form. 

The transition is about 1 volume % or 0.3 linear %.

[snip]

From: Bruce Berger [mailto:bberger at cermalab.co.za] 
Sent: April 7, 2008 3:06 AM

+++++++++

I presume that the 'free silica' refers to this quartz form, and that
limiting it results in a surprisingly smooth physical size change when going
from say, 400 to 700 degrees. Many ceramic materials have a sudden size
shift which I believe leads to micro-fractures and later failure.

Regards
Crispin