Dave Fawthrop wrote:
On Thu, 12 Jan 2006 08:23:54 -0000, "Grumps"
wrote:

| I've always been told that you shouldn't use water as it could crack the
| glass. Is this true or one of those old wives' tales?

There is a standard way of breaking glass bottles cleanly to form a
?glass? using boiling water. So boiling water definitely breaks glass.

It's all about temperature differences surely, and changing temperatures
quickly; the reason glass breaks is because it expands when it gets hot,
and if that happens too quickly the glass won't warm up evenly,
resulting in breakage.

Consider the following:

1. Take a wine glass out of the cupboard and fill with boiling water -
it's unlikely to break.

2. Put it in a pan of cold water and bring to the boil on the cooker -
again, not likely to break.

3. Put the empty glass in the freezer for a while, then remove and fill
with boiling water - it'll almost certainly break, due to the rapidity
of the large temperature change.

David