Re: OOC V for Vicuna
There's a point that you'd have to go out to the wagons to get that canvas and that might not be ideal?
...But there's a counterpoint that probably the wagons are already collecting up lots of rainwater and when it's over you can just go get some. I think Kathkar is looking more at long-term storage? That's what you'd want glass for.
Salves I don't see being in glass. Salves are... coherent, they can be wrapped in leaves or waxed paper or something. (Last Chance Salves are expensive, of course, so they'd be carefully wrapped and packed, but.) Potions I see being in glass, at least until Yrsgrathe introduces single-use plastics.
My impression when you first asked was that you were looking to basically just put a bottle at the edge of the rain, though, and I don't see that getting anything? You'd have to go up to the edge of the cave to put it where the small opening of a potion bottle would actually catch the rainwater. Which is definitely a thing you can and should do, but I say that in the GM-y way. Otherwise, yeah, you need, first, something more open to catch the water. The wagons definitely count but if you want it sooner, I'm sure someone has a hat or helmet or something, like Trilarigas said it wouldn't be hard at all to just lay something out in a vague bowl-shape.
I don't actually know if anyone has used a booster potion recently enough to assume they still have the bottle. But there are several potions in Garl'thak's box, which also might be helpful in other ways. Just keep in mind his general comment of like, yeah, first priority is keeping everyone alive, but also, he's a merchant and these are his wares and like, later, that's something to think about. Especially given that probably the rest of his wares aren't faring very well and he's down a wagon.