Just how waterproof are waterproofs?

An interesting question, and one that causes some grief in some areas- especially with people who are about to part with a significant wodge of cash for a state-of-the-art, high tech bit of gear that promises to be "100%" waterproof on the hill.

So, it will keep them dry, right?
The answer given in a lot of shops is "oh yes indeedy, totally dry. Thats what it does, can I have your money now please"
Wheras the correct answer is more like "well, it will keep the rain off you for most of the time, but the jacket doesn't have any intrinsic magic powers that will repel rain away from you and keep you bone dry all day every day forever."

A pub, the driest way to stay dry

The only true way to keep dry in the mountains is to either a) stay in a pub or b) only walk/climb/run on dry days. As neither of these is a perfect option (sometimes the pub is too crowded), you have to face up to the reality that at sometimes you're going to just have to get wet, or, buy a waterproof jacket.

Buying a "waterproof" has rarely been so confusing, especially with all the types of material out on the market today. Most people will have heard of Goretex, which is the most well publicised of the material (massive marketing budget), eVent is less well known, and then you have the various membranes that are made "in-house" by clothing manufacturers to keep costs down on their jackets, like Hyvent by TNF and Conduit DT by Mountain Hardwear.

Why are there so many names? I hear you cry. Well, the grand-daddy of them all, Gore-tex started by making a breathable membrane through which watervapour could pass, but not water liquid- excellent. They charged people to put it in their jackets- as you would expect. The issue with the original Membrane was that it wasn't entirely sweat proof, and once you sweated in it, the membrane started to corrode, and it didn't stay very waterproof for very long.
This problem was overcome with a PU coating, which gives Gore-tex membranes their longeveity. There are now a number of different types of Gore-tex on the market, Pro-shell, Performance shell and Paclite. (there is also Windstopper, but that is not supposed to be waterPROOF) so we aren't counting it for the moment.
The membranes on each of these are much the same, but it is the FACE fabric and scrim that change, and that is where the cost comes in.
There are different grades of facefabric (the outside fabric) and scrim (the inside fabric) that Goretex produces. Each company gets a swatch and decides which fabrics they want to make their jackets out of. Some of them can cost upwards of £40 a yard, hence why some jackets are more expensive than others.
The more expensive fabrics, if put under a microscope can be seen to have 1 over 1 layers, all over the jacket. This is where each piece of fabric goes over-under-over-under all the way through the garment, with no fraying or imperfection in the fabric. That is what you are paying for with Arcteryx and Mountain Hardwear stuff. Even small imperfections in the fabric can cause waterdroplets on the coat to "burst" and begin to wet out the fabric.

However, no matter how expensive or how cheap the Goretex, they all have the membrane in, so what you are in effect paying for is the fabric on the outside and inside of the garment.
(as a side note, you may wonder why so many jackets with Goretex look the same, or at least have the same design cues- its partially to do with the shape of the body, but also partially to do with Gore- they have specifications for each of the types of membrane with what clothing manufacturers can and can't do. As an example, Gore did not allow people to tape the seams of Windstopper because it isn't "waterproof", and "hybrid jackets" (part hardshell, part softshell) were not allowed to be made with Gore either. They are just beginning to be made by Arc'teryx, but they should have been made a long time ago...)

eVent is much like original Goretex- it is the membrane without the PU coating, and hence is a little more susceptible to sweat. If you have an eVent jacket, you will notice that there is a label inside it saying something like "please keep me clean". This is important. The membrane will be more breathable and just as waterproof as Goretex, but only if you keep it clean. The Pores can get gummed up with sweat and detritus quite fast, so make sure you keep it clean. There is only one type of eVent that I know of (anything else that is eVent, has been re-branded to make it seem like a "new" fabric, when it is actually pretty much the same as the old stuff- helllloooo MHW DryQ) but it works really well. (since writing this I have found out that its actually the film which MHW bought from GE, and used it to make their own membrane- so its akin to eVent, in that it comes from the same background, but its not actually just eVent rebranded.
eVent don't appear to be quite so stuck up about trying things out with their fabrics, and there are a few hybrids out there on the market- waterproof where you need it, less waterproof and more breathable in other places- I haven't tried one yet, so I don't know if its any good.

Other things like HyVent, Omni-tech, H2No etc all seem to be pretty good- generally developed in-house by manufacturers for their products, they don't tend to be as far ahead, technologically as Gore etc. but have some waterproof-ability. All things considered, a plastic bag is waterproof, it just isn't breathable, and that is where a lot of the waterproof fabrics begin to let the user down.

Think about it. If you want a true, totally waterproof garment, a plastic bag is pretty much the best thing you can have. Water doesn't get through plastic. It can't permeate it, and so it must be good.
Yes, to a point. The problem at this point isn't the water on the outside, but the water on the inside, the body is constantly breathing and sweating, and if you stand inside a plastic bag for a while, you will notice condensation building up. This is where the problem comes with less expensive waterproof fabrics. They don't breath enough.
This can also be the problem with expensive fabrics in the wrong climate. Membrane technology pretty much relies upon temperature differential to work. The temperature inside the jacket (you) has to be a certain level above the temperature outside the jacket for the vapour transition to take place. On top of a snowy mountain, where its -25 outside and you are about +37 inside, thats a massive differential, and your jacket will be working optimally.
In a rain forest where its +35 outside and +37 inside, you'll be sweating like a pig and be just as wet from sweat as you will be from the rain. Membrane technology just doesn't work in those conditions.

Finally, just to throw "wetting out" into the mix. Once you have been in the rain for a while, or if you have a particularly old jacket, you will notice that the fabric begins to "wet out". Water no longer "beads" on the surface and it seeps into the facefabric. (this is where some more expensive jackets have a longer resiliance to wetting out than cheaper ones), but they all do it. When the fabric has become wetted out the garment has an extra barrier of water in the fabric which prevents optimal breathability.
So, just how good are the top end bits of gear?

Waterproof testing in Wales

I had the great opportunity to go on an Arc'teryx test event a couple of years ago (another person cancelled, and I was apparently next on the list). There was a minor issue in that all the gear that was available to be tested was XL. I barely fill out an Arc'teryx S  on the best of days, so the XL was totally out of the question. A few other guys were in the same position, and so there was a variety of makes of waterproof out on the hill on the specific day in question.
We were in Wales, scrambling near Devils Kitchen, it was wet. Actually, it was monsoon type wet, a really really nasty day, retrospectively, it was an excellent day for testing waterproofs.
We spent about 8 hours on the hill in driving rain, and the long and short of it was, of about 10 people on the hillin various jackets ranging from £250 to £400, each and every one of us ended the day wet. Some more than others (the less expensive jacket wearers were wet through, but the slightly more expensive jacket wearers were generally damp all over), but none of us stayed dry.

The overall point of this long and somewhat overinflated blog.
If you buy an expensive jacket, its not made with pixie dust. You will get wet.
All jackets have holes in. They have arm holes, they have zips, they have seams. These are weak points where water WILL come in, eventually.
If you buy a cheaper jacket that says "waterproof", remember, so is a plastic bag.
If you buy an eVent jacket, keep it clean.
By the time you are spending £250 or more on a jacket, it doesn't actually matter who makes it, just make sure it fits you and does what you need it to.
If you are balking at the idea of spending more than £250 on a jacket, be prepared to be wet and uncomfortable in really nasty weather. I've been there, and its worth the money, especially in the long term.