Regarding Karo, its not limited to 20PPM. I make 120-160PPM all the time (gel capped) and reduce with Karo.
The issue with Karo is that for non-gel-capped, its a weak stabilizer and only really works for 20PPM. Gel capped, you can go as high as you want.
I don't know where you read that Malto is only good to 40PPM. Here too, you can go as high as you want with the difference being it IS a good stabilizer for PPMs much higher than 20. I routinely make 80-100PPM "naked" and I've had some thats still fine years later without any special handling.
Malto can also be used when gel-capping though Karo works equally well because the gelatine is a fantastic stabilizer of and by itself and a good stabilizing reducer isn't necessary here.
The 20PPM/40PPM limit has to do with the solubility of silver oxide in water. At room temp (75F, not colder) the solubility limit is 21-22PPM. At 150F, the solubility limit is about 40PPM.
If you're producing higher than 20PPM, you need to heat your cell to 140-150F and add the reducer at the start of the run so you get continuous reduction so the rate of production of ionic silver never outpaces the rate of reduction so you never coast over that 40PPM wire. To get a reducer to reduce quickly enough, heat is also required.
The Colloidal Silver particle size the procedures outlined here produce are in the 10-15nm range. Below 10nm, Colloidal Silver can start getting toxic in the body as can colloidal gold (kind of around 7nm or less). Above about 15nm the particles are too large to be absorbed into the blood.
Colloidal Silver at or below 10nm would have a greenish tinge and above 15nm would be tending towards brown/red. "Yellow" puts the particle size into the proper range and its an exact indicator of particle size for a colloid. The colors differ depending on the particular metallic colloid but for silver, yellow is what you want.
I'm not sure what a particle size for IS is, given its dissolved silver oxide. If its dissolved, there isn't a particle size other than the size of the molecule itself.
Silver(I) Oxide is Ag2O
Silver(II) Oxide is AgO
The procedures used here make Silver (I) Oxide which is whats commonly referred to as silver oxide whcih is necessary for making Colloidal Silver given Colloidal Silver is simply a suspension of silver particles in water. Given metallic silver exists as Ag2 (always), I'm not sure what you'd get with reducing AgO nor am I sure you can produce silver(II) oxide electrolytically.
The reducing sugar is oxidized by the silver oxide where this reaction only proceeds in an alkaline environment. The glucose looks like a snake biting its tail (ring) in an acidic environment and as such there is no available reducing group. In an alkaline environment, the "snake" lets go of its tail and the "head" can now reduce something. For something to be reduced, something else must be oxidized.
Maybe I'm mistaken but as far as I know, the reducing sugar molecule can only reduce one ionic silver molecule.
Maltodextrin is a long chain of glucose molecules where only the end molecule at the end of one side of the chain can reduce. These long chains are what make it a good stabilizer.
The size for a single atom of Ag is 0.33 nm though elemental silver only exists as Ag2. Since this size is a diameter, I'm not exactly sure what the atomic size of Ag2 would be. Oxygen is tiny - less than 0.1nm. Obviously in the reduction process the silver particles agglomerate into larger particles in the 10-15nm range if the production is done properly.