If I were to speculate on what makes Collodial silver work, I would assume it would have something to do with ion/electron exchange or that Silver is far less toxic than most other heavy metals.
Establishing that I don't know how it works I'll do my best to stammer through how to make it for you... Basically what you want to do is electrically strip off some silver into distilled water using DC (direct) current. (like the output of most plug in wall chargers) If you use silver as both your anode and cathode you don't have to worry about polarity. Generally what I read indicates levels over 50ppm are necessary from what It looks like 75ppm works well. (don't test your solution while its being charged).
You want to treat the portion of the plant you want to hermaphrodite with a thorough spraying (drenching) of your silver solution on a daily basis until it begins to show male flowers (kindof like rooting clones its hard to predict exactly how long) I read from 10-20 days is the common range. Keep in mind that male flowers mature pretty quickly and once your female becomes fertilized flower development is likely to slow in favor of seed development.
If you don't care about harvesting any bud (to make hash out of, or just to feel humble/modest again) then you might as well start right around the time you start flowering the recipient plants. If you want more flower development before pollination (for any reason) you can push it off for a couple-few weeks. You may want to attempt this on a couple separate occasions so you can get a feel for how fast the plant responds to the silver treatment and how long it takes for your seeds to fully mature..
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If you buy Colloidial silver that is not the right concentration you can resolve this issue with a TDS meter some distilled water and a gals vessel you can boil water in (9in Corning/Pyrex casserole dish)
Take a baseline reading if you solution (compare to concentration on label) then concentrate (distilling off water in a clean glass vessel) or dilute by adding the distilled water..
If you can't come up with 2 pieces of silver, I believe you can use the core of a modern pencil as your cathode (-)
Everything I come across suggests using .999 silver, though I rarely run into much "why" other than: you might get a murky looking solution, or it might cause a little burning on the foliage. Mercury dimes are 90/10 silver/copper and only cost about $1 a piece. (keep in mind I have never personally tried it, but doesn't seem like many people do).