Pedant alert v2.0
No, porcelain is very hard and homogeneous. You can pour boiling water into the thin cup because its coefficient of thermal expansion is consistent throughout. Glass is not- hence the shattering.

However, porcelain has very low tensile strength- it does well in compression, but in tension it snaps pretty quickly, like concrete. That's why it's so brittle.

Toughness is defined as having both a high elastic modulus and a high tensile strength- think of fiberglass reinforced nylon, for instance, which you can find as a fan blade on most cars or used as a fuel tank. You can take a bubble of that stuff that's 1/4" thick, twat it with an aluminum baseball bat and it will just go bouncing merrily away. (Yes, I've done exactly that.)

So: a porcelain guitar would be heavy and look cool, but bad things would happen if you dropped it on concrete.
( The Resident Loon Not a demographic. Do not measure., Thu 16 Apr 2009, 16:19, Reply)