Disclaimer: This water bottle is NOT intended to kill waterborne pathogens, and it should not be expected to make unsafe water potable! The anti-microbial coating is only meant to keep the water bottle smelling fresh. I also see many dubious health claims related to copper water bottles, and I do not personally claim any use for these instructions except making your water bottle less unpleasantly scented. Pure copper containers may actually be effective against some waterborne illnesses, but that's with 16 hours of exposure at room temperature, and the cholera lottery has some really crappy prizes. Oh and copper sulfate is toxic. Rinse very thoroughly.

Reusable water bottles reduce waste, but after a while they start to smell funny. Near-daily cleaning can be required to keep the bacteria at bay. Rinsing with dilute bleach solution keeps the water bottle more sterile for longer, but then your water ends up tasting like bleach. Copper is antimicrobial and kills many bacteria and fungi on contact. Electroplating with copper is relatively cheap and easy, and ordinary stainless-steel water bottles can easily be plated with an internal coating of copper.

Supplies Needed:

Water bottle with a bare metal interior

Copper sulfate (pentahydrate is what I used, sold in most hardware stores as "root killer")

Piece of copper for anode (preferably something rated to be in contact with drinking water, like a pure copper pipe fitting)

12v "motorcycle" battery (or two 6v lantern batteries in series, or a wall adapter that outputs 12V DC)

Three 1/4 watt 1kOhm resistors

Short length of copper wire (look for abandoned appliances by the side of the road and take their power cords to get it for free)

Alligator clips (can substitute clothespins and extra frustration lining up the wire under the clothespins)

Dawn dish soap (because it's the recommended one for getting clean surfaces on brake rotors)

Scrubbing tool (steel wool would be best, but all I had was the world's saddest bottle-brush)

An acid to clean the bottle with (white vinegar would be best, lemon juice should work, and all I had was a grapefruit...)

Stick (look outside) (can be enhanced with optional "tape" to hold wire
in place. Wrapping the wire around 'stick' enables the user to leverage stick's powerful proprietary technology. Turning 'stick' then enables the raising and lowering of an object suspended by the wire. Thank you for examining the detailed description of 'stick')

Step 1: Cleaning

Wash the water bottle with dish soap and an abrasive cleaning tool.

Rinse thoroughly.

Wash the water bottle with an acid solution (in my case, grapefruit juice, though white vinegar is recommended) and an abrasive cleaning tool.

Rinse thoroughly.

Wash the water bottle with dish soap and an abrasive cleaning tool.

Rinse thoroughly.

Don't skip steps here because you want to do things the fast way. The cleaner the bottle, the better the plating will stick. If the bottle is dirty, you'll have to start over and do the whole setup twice, losing the time and energy "savings" from a haphazard cleaning job. The problem with the fast way of doing things is that it takes so much longer!

(If you want to cut corners, only wash the inside, but still, be thorough)

Step 2: Preparing the Electrodes

Wire the copper pipe fitting (or whatever piece of copper is convenient for you) to the positive (+) terminal of the 12V battery. Wire an alligator clip (if you have one) to the three 1kOhm resistors in parallel, and then from the other terminal of the three 1kOhm resistors to the negative (-) terminal of the 12V battery (see picture).

To attach the wire to a 12V battery without clips, you can strip about 4cm of wire, twist the strands together, and then wrap the wire around the terminal and twist it on itself. Using human hands, it will just fall off, but if you can hold it on and give it a twist with needlenose pliers, the connection will be fairly secure.

Step 3: Preparing the Solution

Fill the water bottle with hot water, all the way up past the threads. Pour the water out of the bottle into another impermeable container, like a large glass measuring cup or a plastic tub. Pour copper sulfate crystals into the water and stir until the crystals stop dissolving. Wait around for about 15 minutes during this process to ensure as much copper sulfate goes into solution as possible.

Once no more copper sulfate will dissolve, pour the (now vivid blue) solution back into the water bottle, being careful not to pour any of the copper sulfate crystals back into the bottle. Add hot water to refill the bottle back up to its very maximum level and stir carefully.

(You will need to pour a tiny bit off so that the clothespin/wire or alligator clip does not touch the solution itself. This will force the copper ions to adhere to the water bottle instead of the clip.)

Step 4: Plating the Bottle

Attach the positive wire from the battery to the piece of copper you're using for the anode (in my case, a copper pipe fitting), and wrap the wire around the stick (see introduction for more details about stick). Clip the wire from the negative terminal (that must have three 1kOhm resistors in parallel in line with it, see step 2) to the water bottle. Fill with solution right up until where the solution would touch the clip.

Using the 'stick' (for detailed explanation of "stick" see intro), adjust the height of the copper object within the water bottle. Be careful not to touch the sides of the water bottle with the copper object. If you do, plating will not take place. Place the copper object within the top third of the water bottle, plate for 20 minutes, move the copper object to the middle third of the water bottle, plate for 20 minutes, and move the copper object to the bottom third of the water bottle and plate for 20 minutes. You can plate for longer if desired.

Step 5: Soaking

By now you have a fancy copper-lined water bottle, but I wouldn't recommend drinking out of it just yet. Copper sulfate is kinda toxic. Luckily, it dissolves pretty easily in water, so we can get the traces out. First, put a somewhat excessive quantity of dish soap in the bottle (50mL, say). Add a little hot water and shake the solution vigorously in the bottle. This might help clean it. Somewhat. Really, probably not much at all. The main reason is so that you'll taste the soap if you haven't rinsed well enough, helping you know you got all the copper sulfate out.

Rinse thoroughly with hot water. (Do not scrub. Fill the bottle 1/3 of the way with hot rinsewater, close the cap, and shake vigorously. Repeat six times.)

Fill with hot water, soak for one hour.

Rinse thoroughly with hot water. (Do not scrub. Fill the bottle 1/3 of the way with hot rinsewater, close the cap, and shake vigorously. Repeat six times.)

Following these instructions will leave visible deposits of copper in your water bottle. Despite the many claims on the internet that "copper is always safe for everyone", it's not without risks. The copper deposits will be in the form of tiny crystals with a large total surface area, making copper leach more easily into the water. Copper poisoning is no fun. While it gets rid of the fancy visible layer, you may want to scrub the bottle to reduce the amount of copper to the minimum required for antimicrobial effects.

Also, you probably have spare copper sulfate and an electroplating setup now, so be sure to take advantage of that.