If you are interested in building your own generator, I just finished a really nice unit that has many of the features of the professional generators - constant current ( adjustable ), magnetic stirrer, laser mount, etc...
I designed it for my mother-in-law who was going to use 3-9v batteries, however it seemed like a great opportunity for a new project I could share online with anyone who is interested in making something similar.
You can download all the files needed to build the project at my blog here: morgandemers[dot]com/silvermax-colloidal-silver-generator/
I also put together a nice youtube video of the first prototype being built ( which I sent out to my mother-in-law ) here:
youtu[dot]be/VICuxnBDLEU
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The device produced 15ppm of colloidal silver in 5 hours. The solution was very clear indicating that the particles were quite small - you can see the laser beam test toward the end of the video, or the photos on the blog link above.