Dr. Beck recommends boiling the distilled water immediately before using it to make Colloidal Silver . The reason for this is that it results in the best colloid particle size.
Correct particle size is an important requirement in locking into bacterial receptor sites which prevent them from attaching to and infecting other cells. Using cold water is adequate but if you want to acheive the very best results, boil the water first.
You can tell when you have got it right because the resulting solution is golden in colour which is characteristic of the ideal particle size in solution.
The best utensil to use for boiling is a "glass" one so as to avoid any metalic particle contamination from a metal saucepan.