Stop, WAIT!!! Don’t use the saline!! I did not know this as I was going to do it too.  Please READ!!  BAD BAD BAD - Proper & pure CS ONLY contains 2 ingredients Pure silver & distilled water, NOTHING ELSE. Using salt is DISINFORMATION and dangerous. The method demonstrated on the youtube video is bad on a couple of counts. A) NEVER NEVER NEVER use salt (saline solution) this will NOT create Colloidal Silver, it will create a solution closer to silver nitrate. Using salt in the creative process is what causes skin reactions such as Argyria, a bluish skin colouration made famous by a fuckwit called Paul Karason. People say that the salt acts as a catalyst to start the process, but this is wrong. Use a splash of CS from an existing PURE source it will only be needed for the first time that you make a batch, after your first batch, always keep a small quantity for subsequent batches.  same approach as when making yoghurt, keep some live stuff to start a new batch.  B) The 3 battery method will create a low quality CS product with mostly large particles and black carbon particulates. It will work but is impure and of varying quality. The best method is to use a bench power supply with a "constant current" function. This will allow you to maintain a continuous and constant low current, in the milliamps range to ensure that the particles are as small as possible. There is simply no control when using 3 batteries and there is a strong possibility that the current will cascade and cause carbon deposits on the silver electrodes and contaminate the solution. Again, it is very critical to NOT USE SALT.