I have a whole rant about “waterproof” stuff that I should really just have at the ready for pasting in places.

Basically, people used to use waxed/oiled cloth like canvas. When fresh, it is effectively “waterproof” since the wax/oil is hydrophobic, but as you move, brush up against stuff, etc., paths open up to the hydrophilic underlying fabric, and some moisture can make it through. This leakiness isn’t necessarily a bad thing, because it also lets some moisture out. Over time, you can re-wax/oil the cloth to restore water resistance.

When petrochemicals started getting produced (and/or natural rubber chemistry got better), they made plastics/rubbers that were properly waterproof and flexible: think about rubber gloves. It sounds good to be properly waterproof, but not so much once you understand how it all works as a system.

When you sweat, which you are always doing to some extent, but especially while exercising, your sweat needs to evaporate to dry you off. If you have a waterproof layer on you, your sweat can’t evaporate, so you even without any water making it through your clothing, you end up wet. This is still worth it in some applications like commercial fishing, where the water that hits you would be really cold, while the water (sweat) on the inside is at least warm. Commercial fishing gear is also usually baggy so you can get some evaporation out the waist. That type of clothing is also bulky.

These issue were addressed by the use of non-waterproof synthetics, like nylon weaves, coated with hydrophobic compounds of various degrees of environmental toxicity (these usually just say “treated with DWR”). Better versions have multiple layers, so you could have a layer of a water resistant membrane, a stronger synthetic, and a coating (referred to as 2 layer). The best versions have a third layer to provide backing to the membrane since it’s pretty fragile.

The important thing is these new, lightweight, packable fabrics are not “waterproof”, they are “water resistant”, so they can allow water to evaporate from your body through the fabric. This works because when it rains, the air is at 100% relative humidity (I’m simplifying transient effects), but you are hotter than the surrounding air, so inside the jacket, humidity % is lower, and the water vapor can diffuse through the fabric to outside. The more heat you are generating, the more you can push water vapor out, but you need the jacket to be more permeable. This is a tradeoff, so a jacket designed for running will end up getting soaked through easily if you use it for casual wear, while a jacket designed for casual wear will soak you with sweat if you run in it. The problem is, lots of people want to wear gear meant for hiking cause it’s trendy, but it actually sucks for casual wear. Good brands actually report the permeability of jackets so you can purchase according to your needs.

In my mind, a really good technical jacket would use different fabrics for areas like the tops of your shoulders that need to really shed water vs other areas, but from a manufacturing perspective, it’s not as easy as just grabbing a big roll of 1 material. You could even have volumetric mesh underneath the waterproof fabrics to allow sweat to flow to areas that can let water vapor out.

I think in most cases, people would be better off using either old-school oilcloth/waxed canvas or newer jackets that are actually waterproof for their casual wear, and save the “performance” fabrics for performance. Biking is tough, though. I don’t bike in downpours, so I think my ideal biking rain pants would just be waterproof on the top of the thigh to the knee, something abrasion resistant on the butt, and water resistant everywhere else.

If you remember, could you tell me a bit more about the Marmot trousers? I found the PreCip Eco Full Zip on sale (80-ish € instead of 120€) so I’m very tempted to buy right now.