Waterproof backpack is made of nylon and polyester. Is this fabric waterproof?

Waterproof bag material itself is not waterproof, but these two kind of material made of fabrics, most will be made for water treatment, namely water up to the ball, not so easy to wet, this kind of treatment to get rid of the water in a timely manner, if stays on the fabric, will still wet. There's also a coating that's inside the fabric, so that the water doesn't penetrate into the bag. But the fabric of the general package is not very good waterproof treatment of coating。