A free book with full illustrated instructions for making a resistance soldering iron. The resulting resistance soldering iron is for use by hobby modelers and etched brass kit builders. There are two power settings. The low power setting allow resistance soldering of thin brass without warping or scarring it.
The book describes the electronic parts that you need and gives you links to get them in kit form. It also shows you how to make the enclosure for the electronics. And then there are soldering tips, hints and recommendations.