Hello again sukhoi50,

On the question for electrode spacing the short answer is: Yes
I process my CS with a set distance of 2.75" (to be more precise) between my cathodes and anode. - keeping in mind that my flask is very large (8.x" wide) and so this proved to be the optimum electrode distance for my setup. - yours will likely be different

As for seeding the short answer is: No
However, I would like to try this in the near future in an attempt to improve my solution further as well as help with my theoretical ppm accuracy.

As for manipulating electrodes to maintain optimum voltages, I accomplish this using two strategies. But before I go-on explain these, I'd like to take a moment to explain my setup so that you can gain a better understanding of the design and applications. 

I'm currently processing Colloidal Silver under boiling temps(99-102c). This is done using a 2.2L heat resistant glass beaker with a glass lid(loose seal) over a 750w heated stirer. - I'm using using a 2.5in elyptical stir bar to encourage dispersion during processing. My beaker lid has three holes in it. One major hole in the center which measures aprox. 2.5" AND two minor holes on each side of the center measuring aprox. 1.75"

These holes were designed to fit tapered glass plugs that hold and suspend the silver electrodes in the solution. In the major(center) is a plug containing my anode array which consists of 6 x 10ga loops, whereas the minor holes(on each side), hold the cathode(electrodes), that are also looped and varying in size(dia) and depth. And the reason that I devised this particular setup was a two-fold:

1. It allowed me to swap out my cathode(electrodes) with clean ones during processing - to avoid cleaning stopping and cleaning electrodes, as well as keeping the solution as clean as possible.

2. It allows me to adjust the size of the cathode(electrodes) wetted area by exchanging them as things move along. - to acheive and maintain optimum voltage during processing.

This system allows me I make colloidal silver in three(3) phases by changing out my electrode(each varying in size and depth) to acheive and maintain at an optimum voltage in the cell during each phase. ie, The first set of cathodes(electrodes) which I call No. 1's are made-up of two 12ga full length looped rods suspended in a plug. This configuration helps promote maximum exposure in ther cell on startup. As the conductivity of the solution is quite low. Of which I'd add, the water must be brought-up to temp beforehand AND more importantly.. prove to be completely free of all visible bubbles(oxygen) on the electrodes before turning on the circuit. This is critical to the optimization of the bulk fluid so as to minimize oxidation and maximize conductivity. Of which I'd add, results in a startup current load of 1.5 out of 8.5mAh in my own case. 

Having said that, once the circuit is activated, the amperage will rise until it reaches the set limit of 8.5mAh( in my case), after which, the voltage drop will begin to register. At which point, I let the process run until my load voltages dop bellow 13v. At which point, I pull out the cathode(electrodes) and swap them out with my next set(No. 2's), and begin the next phase of processing. Which takes aprox. 18mins. in my case.

These No. 2 electrodes are made-up of 14ga looped cathode(electrodes). Which have been adjusted in size and depth so as to get me as close to 27v as possible upon entry. I achieved this by trial and error, as I also wanted to work it out so that this phase would end just short of my own tolerances for oxide accumulation on the cathodes(electrods) AND... of course, as close as possible to my 13v limit. - case and point. It can be done!

Once my No 1 and 2's are done, I then move to my final No 3 cathode(electrodes), that are made-up of 24ga loops with very shallow in depth(no more than 3" wetted). Which btw. only takes about 7 mins. before reaching maximum entrophy. - AKA my 13v limit. - After which, the batch is complete and ready for cooling. 

In conclusion I'd add that I devised this setup in an effort to automate my colloidal silver processing, and improving repeatability. To which I'd add, has proven to be very successful. However, I'd also add that before I upgraded to lab grade equipment, that I had devised and used this very same processing method with common household items safe the heated stirrer(Which was purchased on eBay). Though it remains that everything else was purchased and put together on a limited budget. And so if you're interested in seeing my parts list and assembly notes on that, I'd be more than happy to share. 

~

On the topic of voltage and resistance, I wanted to add that these levels are proportionate to your electrode exposure. And so if you're finding that your processing is taking far too long to be tolerable. Then I'd recommend looking at increasing your electrodes(dia) OR perhaps a cluster formation, OR even both. ie, you can mount or suspend multiple electrodes on a silicon grommets such as shown bellow: 

Thhis will raise the conductivity between your anode and cathodes and help move things along the full . potential of your anode. Though I'd caution against overloaing your anode(see: theoretical maximum based on total surface area). And add that it is preferable that you keep your cathode dia. and/or exposure inferior to your anode, which allows for headroom(or flexibility) in controlling your voltages during processing.

Hope this helps.

PS. Using this method, I make 2L of colloidal silver measuring aprox. 18ppm in approximately 45mins