I know that wearing a plastic bag over your hand will make it 100% waterproof, but it will also block air, so it won’t be breathable, and thus your hand will feel like its choking, and it will get moist and hot easily. Aren’t waterproofness and breathability inversly related? i.e. you can’t have one without the other? (I know an exception can be a raincoat, but that’s only breathable by its shape, and also its shape only protects you from getting wet from the rain, usually from above. But you won’t be 100% waterproof if someone hosed you with water)
There are lots of jacket companies out there claiming they can do both.
How can you have both? How can you have your cake and eat it too at the same time?
In: Engineering
there are somewhat exotic materials and constructions that can stop liquids but allow gasses to pass through, but in the case of clothing it’s fairly straightforward.
the material of a jacket is mildly hydrophobic so the water doesn’t stick as readily, and it is woven in a way so that, as it hits the jacket and moves down, the water isn’t pushed into the jacket.
this, combined with the small amounts and pressure encountered in the rain mean the water would rather stay as a drop and roll off, rather than squeeze through the gaps in the fabric.
The membranes of jackets have pores in them that are too small for liquid water to pass through, but will allow air to pass.
The breathable part comes from things like flaps on back that let air out but not water (coming from above in), vent holes in arm pits where, again, falling precipitation won’t enter.
I never thought I was smart enough to answer any questions that are asked in the sub, but this one I can explain in my sleep.
If you zoom into a waterproof jacket, it will look as if it’s a net. The holes in the “net” are large enough for air molecules to pass by. Water molecules are larger than air molecules and cannot pass through the net.
So a jacket, can be waterproof (preventing water from crossing the material) and breathable (allowing air to travel through it) at the same time.
I know this because I make and sell cloth diapers for a living. Lil Helper Cloth Diapers!!!
The outer shell of modern cloth diapers is much like a jacket, but worn inside out. Where you want to contain moisture (pee and poop) inside the diaper, where a jacket is supposed to keep moisture from coming in.
To illustrate this point, I took a video while visiting a trade show in China that shows a waterproof material that is also breathable: [https://www.youtube.com/watch?v=9zL9sSxrw6E](https://www.youtube.com/watch?v=9zL9sSxrw6E)
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