Hydrosols

v

Filteration for Particulate Matter

It is advisable to fill very large containers of hydrosol upon their arrival. First, this will remove any particulate matter, reducing the substances that can carry bacteria, and second, you are more likely to notice any contamination, molds, and the like that may already be present. 

The many methods of filtering waters are described later on, but at the very least a paper filter, such as unbleached coffee filter, should be used. Paper filters are easily sterilized by a very short blast in a microwave oven. Microwave them for only one to two seconds at a time, until you know what your oven's power is like. I prefer not to use microwaves at all, but as a means of sterilizing things they have some use.

Reference: Hydrosols: The next Aromatherapy: Suzanne Catty