PPM (WHAT IS THE DIFFERENCE)
The different types/kinds of water that folks use to brew colloidal silver, and the different PPM measurements. It's actually very simple: When you brew CS with electricity (what all the CS brewers do), if there are any minerals/substances in the water you are brewing, the silver particles will join themselves to those mineral/substance particles. This will result in much larger particles of this silver-mineral combo; so big, in fact that they can be seen with the naked eye in the form of cloudy/murky water. The higher the mineral/substance content in the water being brewed, the cloudier the water will become, and the faster that will happen. Some mineral-rich (or polluted) water will look like rinse water from a washing machine in 10 minutes. Other water might take 20 minutes to look just slightly cloudy. The only waters I know of that are entirely mineral-free (and brew crystal clear CS) are de-ionized water, water from a 5- stage reverse osmosis unit and, of course, steam distilled water. When a person cannot access any of those mineral-free waters to make CS with, I always say, "Brew it 10 - 20 minutes, or until you can't see your hand on the other side of the jar (because it's become too cloudy)."
How good is this cloudy CS?
I heard a story of missionary in India who was brewing CS using water from the Ganges River (nothing else available) and having great results using it against all sorts of pathogen-caused diseases in his clinic. (He told me, "That's how we sanitize the water - we brew CS in it!")
This brings up a related point: PPM
I think it's a human characteristic (plus pharma programming) to feel that, if a small amount is good, a larger amount will be better. As anyone in the homeopathy field can tell you, that is frequently the opposite of the truth. UCLA Microbiology Dept found silver to be fatal to pathogens at 2.5 ppm and absolutely fatal at 5 ppm. 10 ppm was a tiny bit better, but anything stronger was in no measurable way more effective. No research anywhere has indicated that higher ppm is more effective than 10-15 ppm in killing pathogens. Dead is dead. Killing an ant with a sledge hammer is not more dead than with a tiny hammer! (Or your fingertip!) The important thing here is not how much silver is present, but how tiny the silver particles are.
ABSOLUTELY, HIGH PPM CS DOES NOT KILL PATHOGENS ANY BETTER THAN 10 PPM, and probably less effectively because the particles are so much larger and cannot get to the same locations within the body (such as inside the body's cells, where viruses like to hide) that very tiny particles can. "More is better" applies to number of particles, not size of particles. "Smaller is better" applies to good CS.