This is my cheap soldering iron controller for the benefit of hackaday readers in response to this post.
It is simply a cheap lamp dimmer, wire nutted to the cord about 8″ back from the plug. It works very well. It was borne out of a need to solder thin paper phenolic boards without causing them to delaminate. The iron is only 30 watts, well below the dimmer’s rated 600 watt maximum.