How do I measure concentration with cheap device?

I have 3 nine volt batteries in series (red-to-black) and two pure silver electrodes. So how do I measure the concentration of the silver colloid? Is there a non-light light test? You know, one that won't turn the silver black or knock it out of solution by light exposure but will gauge the concentration by light penetration? Ultraviolet? Infrared? I just use the silver water maker for about three minutes in distilled water because it takes a long time to start "cooking" in distilled water with no salt. So it's only actively going for about thirty seconds. Any ideas as to how to measure concentration? Test strips? Is this an O.K. way to make silver colloid on the cheap? It makes clouds of white in the water. Thanks and God bless.