No, the cotton duck isn't waterproof. They are lying, and the thousands of people who have been using it for decades only use it because they are sad deluded hipsters. Or maybe it is a conspiracy (like the moon landings).
Of course it is waterproof.
Do you think they would have had a successful business using the same fabric for so long if it didn't work?
Blimey, steady on! It seems like an honest question (and I don't think I could claim it is 100% waterproof, given what that actually means).
Cotton Duck fabric is waterproof in the same way as a Tent canvas. The density of the cotton means that, when it gets wet on the outside, it expands to form a barrier to the inside.
I've left my bike in the rain for hours (almost always at the YHA on Bryan Chapman funnily enough). The fabric is sodden on the outside and bone-dry on the inside. I've NEVER had water get through to the contents.
I have 2 Barleys and a Super-C.
They've taken a real beating over the years and look better for it. You can cram things in, and lash things to them, in a way you can't with Ortlieb..etc.
I have Ortlieb panniers and Bar-bags. They ARE waterproof because they are heat-treated plastic and form an impermeable barrier.
If you are carrying a bar-bag into a Cafe then personally I'd get an Ortlieb because you can wipe the water off. A Cotton Duck barbag would hold water be damp to the touch.
My camping gear, being Ortlieb can be left out in the rain, thrown onto wet grass...and my front panniers, being roll-tops, could probably survive being dropped in a river.
I can't confirm this but I would assume Cotton Duck could become damp inside if, say, you left panniers on very wet grass or in a puddle.
