Step 1: Supplies
--Water bottle: A Nalgene (what I use here) or a metal water bottle will work best, but all you really need is any container that will hold water.
--Iodine Tincture Solution: You want Iodine Tincture with 2% Iodine and about 47% alcohol. Bottles of this solution should be available at your local drugstore and a 2 oz. bottle is usually $3 or less.
--An eyedropper: Counting the number of drops is the easiest way to keep track of how much you're using.
--A good water source: This can be a lake, a river, a stream, etc. If you have a choice of water sources, consider these two tips:
Clear water is better than cloudy water.
Flowing water is better than still water.
Remember, though, that even if the water looks extremely pure and clean, it should still be purified before drinking. Looks can be deceiving!
Step 2: Fill Your Bottle
Examine your bottle of water to make sure there are not too many floating particles (called "floaties" in scientific terms). A couple of small floaties are fine, but too many large floaties can be dangerous. If this happens, you need to try filling up again. A way to solve this problem is to cover the mouth of the bottle with a bandanna or thin cloth that will allow water into the bottle but keep floaties out.
Step 3: Add the Iodine Tincture
The water source: if your source is a lake or some other still body of water, you want to add closer to 10 drops; if the source is flowing, you can add fewer.
The clarity of the water: you should add closer to 10 drops if the water is cloudy.
Your own aversion to the taste of iodine: some people hate the taste of iodine (it is a little bitter, and you will notice the taste in your purified water). If this is the case, you might want to add closer to 5 drops.
Personally, I'm a fan of 8 drops. If you are filling up a bottle or container that is not 32 fl. oz. or 1 liter, change your measurements accordingly. A 2 liter bottle will require twice the number of drops.
Step 4: Wait 5 Minutes
Step 5: Thread the Bottle
A little water will probably leak out while threading, and that's not bad--it just ensures that you've fully threaded.
Step 6: Wait 30 Minutes, Then Enjoy!
After you have waited 30 minutes, your water is purified for drinking. Revel in the cool, clean taste of your iodine-infused water while you enjoy your wilderness adventure.