Coolant additives tech article for discussion.

[vex]

Simple testing fixture could be had/built for minimal effort thereby reducing human error:

Pressurized system with a compressor and Schroeder valves. Add in a shaker table (or duct tape an old phone to an old radiator pipe), plumb in a heat exchanger and a butane burner, and you could simulate it a lot more accurately.

Contrary to Ted's thought, I think distilled water should be the base line. Another control would be what Ted suggested as a base line. Though all things being relative, the baseline should probably be 50/50 mix as that's generally what's in each and every car.