I still have several of the old soldering irons here. I used them at work as a sheet metal worker on occasion. They used to be used much more often in older days, but with the advent of modern welding equipment which works so well on thin metal, the need is reduced to copper and brass. We little natural gas furnaces, which were designed for the job. But you had to constantly wash down the contact surfaces of your work piece with acid, and when you hit that acid with the iron, you QUICKLY learned to avoid breathing the smoky fumes which rose from the iron! And then you melted the lead/tin alloy solder, which added more toxic fumes. And then you added more and more and more acid, to keep everything "clean" for good solder joints. It would take days to get that sour acid taste out of your mouth and nasal passages. And if you got too many heavy whiffs of that acid smoke, your lungs would react with violent pain, and you had to go outdoors and catch your breath for a few minutes. When it got better...you went right back to work. After a long day of soldering joints, the copper or brass rivets in your blue jeans would be corroded green, any plated steel zippers, rivets, etc in your clothes would start to rust, leaving stains on your skin on the inside, where you perspired against them.
So... Anyone wondering why soldering and body lead work is becoming a "lost art"?