On Mon, 07 Jan 2008 06:28:10 +1100, Trevor Wilson
wrote:

Why the yellow flame, before the blue flame on the glass?

So as not to crack the glass through too-intense local heating. Much
less risk if you bring it all up to a fairly high temperature before
getting serious with one bit.

**OK, that makes sense. Wouldn't holding the blue flame further away
achieve the same thing?

The blue flame further away wouldn't reach the work.