When you're in the wilderness, you need clean water to drink -- but water sources in the wilderness can carry bacteria such as giardia. You don't want giardia, trust me, and trying to carry a few jugs of Poland Spring would be extremely heavy and inefficient. Luckily, there are a number of ways to purify water, and one of the simplest, cheapest, and most effective ways is to use iodine tincture.
Step 1: Supplies
To complete this task, you'll need the following:
--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
After finding a water source, you need to fill your bottle with water. To do this, position yourself close to the water source and tilt the bottle under the water. You want to collect water from near the surface, so don't just immerse the whole bottle in the water. Let the bottle fill up and remove it.
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
Dip your eyedropper into the iodine tincture and squeeze up some of the liquid. Carefully position the eyedropper over the mouth of the bottle and add 5-10 drops per 32 fluid ounces (about 1 liter) of water. The exact number of drops is a personal choice (I can't make this decision for you) depending on the following factors:
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
After adding the iodine, you need to wait 5 minutes before you can continue. You can go for a quick hike, admire nature, play a game, or think up an idea for your next Instructable.
Step 5: Thread the Bottle
After five minutes, you need to purify the mouth and rim of the bottle (which touched the original water source and which will touch your mouth). To do this, you need to "thread" the bottle. Turn the bottle upside down and slowly unscrew the top until you can see a ring of water appear around the inner rim. Once you see that ring of water, you know that the water with the iodine has touched the mouth of the bottle and disinfected it. Screw the top back on and flip the bottle right-side up.
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!
The iodine needs time to completely purify the water. You need to wait 30 minutes before you can drink the water--plenty of time to finalize that idea for an Instructable.
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.