As I suspected, you can't get enough watts out of 4 AA alkaline cells to solder anything much heavier than a small printed circuit pad.
A friend's wife gave him one of those "Cold Heat" soldering irons as a birthday present last Sunday and we tried it out at his party.
With 4 fresh alkalines installed it couldn't tin the stripped end of a piece of No. 18 stranded wire copper wire.
Not a very practical tool for anything but very specialized lightweight work. Looking at some typical battery curves I'd estimate that it probably doesn't put out more than about 6 watts on fresh batteries.
The tip, about 3/16" diameter and cut on the bias, was made up out of two nearly half round pieces of what looked like carbon separated by an insulator which stopped short of the end.
It also was difficult to keep both sides of the tip in contact with the workpiece, which of course is needed to get any heat at all.
On a scale of 1 to 10 I'd give it about 0.5.
Jeff