I mentioned "Specific Heat" before, and it's so important, I want to
expand it. Nobody much uses the term, but we all deal with it on a
daily basis. People tend to think that if you heat something up, it
gets hot. That's not precisely true. Jim Binnion talked about BTU's
on a related thread - they are a more common unit in the real world,
but specific heat is measured in calories. One calorie is the amount
of energy that it takes to raise one gram of water by one degree
centigrade. That is also the definition of specific heat - that the
energy required to raise one gram of water by one degree is one
calorie. Every substance in the universe has it's own specific heat.
Thus, if you line up many things, you'll find that one calorie will
raise the temp. of this by 1/2 degree, that by 1 1/2 degree, etc.
What this means in our world is pretty simple, really, but essential.
When you get a silver bezel and solder it to a brass plate, you get
your torch and apply heat. So, we're heating, heating - oops, the
silver's getting too hot, move the torch over, etc. So, both pieces
are good and hot, we solder them, flow it, etc., and we're done. As
long as you stay at heat, everything will be fine, because the metals
were actually heated separately. Cool it off, and now we have
something that will behave as a unit - as one. The metals are
"married" - they are bonded together, but still retain their own
properties. Now, we need to reflow the solder. Let's suppose the
specific heat of silver is 2, and that of brass is 1 - made up
numbers, but it's a proportion. So, we put 200 calories of heat into
the piece. That means that the brass is rising in temperature by 1,
and the silver by 2. When the brass is at 500 degrees, the silver is
at 1000 - that is what specific heat means, and why it's important in
metal work. Realize, too, that this is separate from conductivity -
the ability of metal to transmit heat. Even nonconductive materials
still have a specific heat. This is the reason why asbestos does what
it does, and why it seems to take forever to get a steel rod red hot.
And it's why silver soldered to brass and other things seems to just
go splat all of a sudden.