>>2657767If you want to forgo all synthetic materials, you have frankly very few options for rain protection.
>Ventile/ETA proofNot fully waterproof, but sufficient if you're wearing enough wool underneath. Mind you, it eventually wets through and becomes cold. Again, wear enough wool underneath.
>Wool Wool is water repellent to a certain degree. More so if it is treated with lanolin and the right kind of fabric - either densely woven gabardine, or densely felted and unidirectionally brushed melton (called strichloden in german). Traditionally, strichloden was worn as a cloak, not as a jacket - if the cloak gets wet, the layers underneath don't immediately absorb the water. Early trench coats were made of wool gabardine, maybe it works a bit better.
>Waxed cotton/natural rubberFully or almost fully waterproof. Better worn as a cloak, rather than a jacket, since it is also not very breathable.
On balance, if I had to make a choice I would wear wool as top layer, and treat it with lanolin to be a kind of softshell. Then I'd carry a waxed cotton poncho in case of rain. I wouldn't trust eta proof in extended rain, but I frankly don't have experience with it so maybe it does work after all.
