Thank you for the video. It is interesting and gives me some ideas. I like the idea you have with the heater which would get around the need for a heating magnetic stirrer which I do not like the idea of because of poor shielding. I might be able to incorporate the idea into my design but so far I have not been able to find a similar heater. What would that be called?

Thanks for your feedback on the video.

Searches keep bringing up all manner of things such as kettles and electrical heaters but nothing remotely close to what I am looking for.

The heater I am using is quite common in Brazil, but possibly hard to find in other countries. In Brazil it is called, in portuguese language, "ebulidor de água" (official name) or "rabo quente" (popular name). It is not a very safe heater (cannot be used inside metallic pots, must be kept under immersion always, the water cannot be touched because of the electricity). It is available for purchase at www.mercadolivre.com.br  (the Brazilian ebay clone).

I think many models of immersion water heater at ebay will work fine.

It might be easier if you added a temperature controller to control the heater so you do not have to keep monitoring it. There are simple temperature controllers on Amazon and eBay to control temperature and monitor the temperature. STC-1000 is one which is fairly inexpensive and there is a new firmware available for certain models which provide better control of temperature such as different temperatures at certain times which is not available with the regular firmware. It might come in useful if you do any fermentation.

https://github.com/matsstaff/stc1000p
The place to purchase the correct ones which can be firmware updated can be found on those pages. I want to get one myself when I can.

I am not sure if there is a need for a thermal controller. There is a physical limitation, the water-bath temperature never will be higher than 100°C (212°F). And because the water-bath covers only 1/3 of the distilled water glass, the distilled water temperature will be slightly lower, around 99°C (211°F), that seems the ideal; near the boiling point, reducing the water ability to retain adsorbed gas, but without create vapour bubles.

The water heater I am using now (and visible in the video) is too powerful (750 Watts). This is the reason it requires some supervision otherwise it spread the water-bath water everywhere.

The previous heater, that worked for several years, but died, was weaker (~200 Watts) and was possible to keep it running over all the colloidal silver production time, without any supervision.

It would be a good idea to implement some form of stirring because that keeps the quality high. It's difficult to maintain quality ie avoid agglomeration without some form of stirring.

I have no experience with magnetic stirrer. It requires a more specialized and professional equipment for the colloidal silver production and - maybe I am wrong - seems it spread the silver oxide inside the distilled water, while I like to keep the silver oxide bonded in the silver wires to remove with a paper towel.

In fact the method shown in my video has a stirring without mechanical parts. It is a kind of "soft stirring" by thermal convection provided by the water-bath covering only 1/3 of the distilled water glass.

The distilled water heats up when in the bottom and go to the glass top; there, in contact with the air it cools down, becoming heavier and falling to the glass bottom, repeating this cicle over and over.

I have a good experience with this stirring and the colloidal silver collor is always homogeneous at any given point of the production process, as can be seen in the video.