I was taught to use it by people that use it religiously for their
work. I don't know if the aluminum has any effect on the castings. I
haven't had any problem yet and I haven't heard them tell of any
problems. I like it because, as you said, it cools at a slower rate.
I melt it into RTV molds with a soldering iron or wax pen. It allows
me to be sure to remove all bubbles in the mold.
But the thing I like best about it is that I can warm it with my
hands and work it repeatedly. It is very maleable (sp) for very
original designs. It is tricky to ensure it keeps its shape for
casting, but I think cooling the set sprue tree would solve that.
And it smells nice too.
If anyone has had any problems with the aluminum in casting, let me
know. I think it is used in dental casting, though I'm not sure what
is cast with it (gold?).
But the people who taught/teach me use it in their classes for their
students. So if it caused problems in casting, I would think it
would show up in failures of their students' castings. I haven't seen
it in the 3-plus years I have been with them.
But it's an interesting thought to pursue.