Martin, I don't agree with this. If you look at the Overall Heat Transfer Coefficient the conductivity of the metal is the lowest resistance in the circuit. If you heat with fire, the gas to metal has the highest resistance, the liquid is the next highest. If you run the numbers, there is negligable time difference. I actualy ran a test for 2 pats I had that were the same size and geometry. One was SS and the other was AL. The SS kettle got to a boil faster! I expected the AL to be a little faster. I think it was due to more bubbles in the AL acting as insulators (rougher finish) and more loss of heat through the side walls in the AL.
Aluminum will spread the heat better so you avoid hot spots.
Thanks for the info, Jeff. I'm always interested in learning more from someone that knows better!
I'm assuming that I should still be quite concerned with heat loss through the Al kettle walls. Last night during testing, I had water boiling at the normal 212F and did a surface temp check with an IR thermometer and it read about 110 to 120 F. I'd say that insulation will be a desirable thing for that electrically heated kettle. Does anyone know if the aluminum-foil backed plastic bubble sheet insulation is heat resistant enough to handle 200F+ ?? I don't have the manufacturer's information on the remnant of the insulation roll that I have to check for this info. I was thinking that a couple of wraps of that bubble sheet with a velcrow seam would make it easy to install and remove as needed for use and cleaning.