http://www.nansupacks.com/pp-w....oven-sack/fertilizer
Are woven polypropylene bags waterproof?
Tightly woven polypropylene is highly water repellent and weatherproof. However, because it is breathable, moisture from the air can still enter unless an additional coating or waterproof repellent is applied. Fully waterproof and washable coatings can be applied to either the inside or the outside of the material.