I just finished soldering a #6 wire to a copper connector. I am out of
propane see used a carbon rod and battery charger to heat the copper
connector. All worked well, but now I wonder, all the heat starts at
the contact point.
Is there somthing about carbon that causes a high
resistance at the contact point?
Does it matter what it is contacting?
Thanks, Mike

On Fri, 8 Feb 2008 12:46:28 -0600, "amdx" <amdx@knology.net> wrote:

>I just finished soldering a #6 wire to a copper connector. I am out of
>propane see used a carbon rod and battery charger to heat the copper
>connector. All worked well, but now I wonder, all the heat starts at
>the contact point.
> Is there somthing about carbon that causes a high
>resistance at the contact point?
> Does it matter what it is contacting?
> Thanks, Mike
>
I have a soldering set from the 50's that consists of a largish open
core transformer and a set of carbon rods. It is a good way to solder
heavy things like auto radiators.

Carbon/graphite is a semiconductor and has a relatively high
resistance compared to metals - the size of the contact point and
current available determine the heating.

Does it matter what it contacts - yes won't work on insulating
material obviously. Doesn't work so well on steel - at least my
device doesn't. Good for heating non ferrous metals.
--