Re: How long to brew homemade colloidal silver?

You should really add a current regulating diode to your circuit. Otherwise, you'll have no way to control the amount of current provided to the electrodes as the conductivity of your solution rises during processing.

That said, I'd recommend starting off with a .75 - 1.5 mA current regulator to begin with. After which, you could stack these in parallel to raise the current level should the need arise later on.

With regard to your question, the most common approach in home brew silver solutions is to go about it by eye, and work from your results. ie, you can run the process until your solution changes color(amber) which usually indicates that you're nearing the maximum saturation point(aprox. 16-18ppm), and use this as a benchmark for future reference.

For example, assuming you're solution reached a maximum saturation in 4 hrs, 22mins. You could then run your next batch to aprox. 4 hrs and 15mins so as to hold short of the point of change, which in turn, will help maintain an optimum in terms of particle size and density.

That said, I'd remind you that this can only effectively work if you make use of a current limiter. Otherwise, the current in your circuit will quickly overload your electrodes, which will in turn break-down your solution prematurely at the cost of your PPM potential.

Hope this helps