Any zapper, because it has a pure DC output, can make Colloidal Silver .
Usually, low voltage generators of Colloidal Silver use a voltage of around 30V, and good ones have a constant current source of around 1mA or less, to make good quality Colloidal Silver from 99.99% pure silver.
In an emergency, a single 9V battery can be used with some kind of “ballast”, as suggested on the Plant Grown Stimulator” of Bob Beck
To make a 8_oz of colloidal silver with pure distillated water and a 9V zapper as the Orgonite Africa, takes several hours to have a 5 to 10ppm. If you know what this solution tastes, OK, if not, stop when the water starts having a slight bitter metallic taste.
Use half of the liquid, and keep the other half to make another 8_oz. This “seed” will make your new colloidal silver MUCH faster.
Zappers having a 1k_Ohm output resistor will have, close to the end of the process, a current of 7V/1k_Ohm, up to 7mA. Really too much for a good result.
MZ3b, of Maestro-Zapper, has an adjustable constant current source that can be set for only 2mA. With the 30kHz frequency, 57% duty cycle, you have almost perfect conditions.
The only function missing is an automatic stop when the right ppm is reached. Some day…
To try colloidal silver, to experiment with, or on an emergency situation, a zapper can make your happy day. But for a regular use, a dedicated colloidal silver generator is recommended.