I thought I would make some comments on the design of boilers and the desirable material properties. My experience with boilers started with building my first locomotive. Like many live steamers initially I was more interested in the machining side of the things. I had that locomotive running on air and needed a boiler. I wrote to a gentleman who advertised in Live Steam magazine and he quoted $600 to build my boiler. Well, $600 was an astronomical sum to a college student in the mid-70s so I figured I would build my own. I ended up building one in steel with copper tubes; I paid the best welder I knew $125 to weld it up for me. That experience grew into a life-long interest and career. My comments are based on 30 years of building, inspecting, operating, and maintaining boilers.