Clamp it

In order to solder the wine charm in place, it's important that (1) it is held steady while looped around the wine glass stem, and (2) that there is minimal amount of thermal contact between the wine glass and the soldering iron. Using a "helping hands" soldering tool provides a good solution to both problems. This is part of a DIY "solder your own wine charms" project; read more about it here.