I've never worked with platinum wire in this way so the question
is: Does platinum ball up at the ends like gold and silver?
Well, yes. And no...... First off, it's required that you have and
use welding glasses or goggles to melt platinum. And if you get a
wire hot enough it will ball up just like any other metal. Problem is
I guess you want to push it on a flat surface while it's molten, as
people do. That you won't be able to do, as the metal when freeze
pretty much the moment you remove the heat. You could ball the end
and then file your flat spot. I'd probably melt a ball and then
solder it on the end of a wire. You're going to need a platinum
crucible - you can't use a standard soldering pad and absolutely NOT
a charcoal block......