On Sat, 04 Feb 2006 07:35:05 +0000, Gary Wooding
wrote:

Don Foreman wrote:
On Fri, 03 Feb 2006 14:02:24 -0600, Don Foreman
wrote:

snip....

BTW, re recent discussions of propane vs O/A for silverbrazing: The
two joints on opposite sides of the 3/4" dia hub were made with the
same brazing material (Easy-Flo 45) at different times. The
concentrated heat of O/A allowed me to have the second joint made
before the other side of the hub got hot enough to soften the previous
joint. Can't do that with propane, gotta use different brazing
materials of different melting points.

I beg to differ. Hard soldering (silverbrazing) is a primary process in
the manufacture of handmade jewellery; something I've been doing for
over 40 years. I frequently need to solder _very_ close to an existing
joint (a few millimetres) and have observed that the new solder melts
before the old stuff, even though its in the same propane flame. The
difference is not great but its certainly there. The process of melting
the solder changes seems to change its characteristics and raise its
melting point. I use this property a great deal and seldom use different
grades of solder.

And this on highly conductive metals like silver and gold. Man,
that's what I call heat control! I'll bet 40 years of experience
doesn't hurt a bit.