On Mon, 16 Jan 2017 11:02:17 -0800 (PST), wrote:

is a stained glass iron use able for rosin core solder on copper?

Stained glass assembly uses lead, so any remenant will be compatible
with 60/40 solder and flux.

High wattage irons are useful in soltering heavy gauge mounting tabs
and screw posts, in closing sheild seams and in other types of heavy
copper soldering. Raising the temperature quickly, completing the
soldering and removing the heat source within the thermal time
constant of many power semiconductor packages is impractical with
smaller irons.

RL