I've had a question from one of our readers about the difference between waterproof and water repellant fabrics, so that she could figure out what to use to make some travel clothing for her kids.
I tried writing about this and found myself wandering round and round in circles getting myself more and more confused. So instead I'll send to you someone whose knowledge I really respect: Roger Caffin, at www.bushwalking.org.au.
You can find really in depth, thoughtful information on the following page (with lots of links to more pages):
Sorry, I tried to do it myself, but why reinvent the wheel?