Wow, you lot are a busy bunch.
I use sterile rolled cotton from CVS. It is cheap, I do not boil it but probably should. I could actually pick a life times supply right down the road and sterilize it myself if I was that concerned. Any crops grown where I live have to be grown using "organic pesticides" so they all qualify for the organic label. Ground water preservation and all....
If it is white it is bleached using one method or another. Cotton is not bright white naturally. Boiling in distilled water and rinsing in distilled water will get rid of most of the residue of this. If you are boiling in tap water... My thoughts are you should just use it out of the bag.
I also find wick preference to be heavily reliant on the end user. I have a small army of IGO-W4 drippers, all coiled basically the same except for the one with mesh, all with various wick materials. I find I like cotton best, second is Silica, to me silica and ekowool are the same. The exception here are a few juices that I really like on stainless wick. My son prefers silica over cotton and hates stainless anything.
TLDR: use the cotton you are comfortable with, if you are going to spend time boiling it use distilled water, or at least RO water from a maintained RO system.
CVS Rolled Cotton - CVS pharmacy
http://www.walgreens.com/store/c/first-aid-sterile-absorbent-cotton-roll/ID=prod6148835-product
Swisspers Organic Triple Size Cotton Balls | drugstore.com