Dome/Door height ratio with

[david s]

No that is known as quartz inversion and occurs at a much lower temp (537 C) Vitrification is the silica in the clay body beginning to melt in company with fluxes like iron and lime, to render the clay body impervious to water, like impervious china toilet bowls, stoneware or porcelain.

[david s]

Next time you take a pee you may notice "vitrified China" on the toilet bowl. This is specified so the clay body is impervious, thus reducing the ability for little germies to harbour in the material.

[dmun]

My art ceramics background leads me to use the looser definition of being fired high enough to be insoluble in water

I've been requested to point out the clay isn't water soluble, in the way that sugar is. It will turn into a mud puddle in the presence of water, but not dissolve.

An explanation:

http://pottery.about.com/od/temperat...p/tempclay.htm

Thanks, David.

[david s]

http://pottery.about.com/od/temperat...p/tempclay.htm

This is the appropriate page to read on the link.