Answered.. Closed. Micron filters are obviously the best choice, and there are myriads of threads about this subject. In the case of not having microns available, tightly balled cotton is your best bet. Though definitely not as good as micron filters, cotton can still filter crap out that's bigger than ~45-50 microns. Cigarette filters would work, but aren't the safest or most sterile product you could use.