"Makes sense." He does that; it takes a couple tries to get the cork in without letting too much air out, but then he has a puffy waterskin.

Sandra looks at it. "All right, what happens if you do the reverse weather-barrier on it now?" 

He sets it on the floor and sucks some heat out and it stops being puffy!

"Whoa." Sandra stares at it with fascination. "Hmm, we could - put a string around it with markings to measure how fat it is? And then that'd be sort of a way to measure the temperature, if we put it inside the glass box. What happens if you make it hotter than the room?" 

"Well, my guess is that it will puff back up and then spring a leak, but if we got something that could handle more heat and more pressure and just keep expanding that could work."

"Right. I'm trying to think what kinds of material would be strong but springy enough..." 

"Yeah. Something like a spring, but a container . . . Oh, here's a thought, what if we had a glass container with a long neck, and some kind of stopper in the neck that could slide up and down without letting air past it? Then we could see how high the air pushes it."

"Ooh. It'd have to be a really slippery stopper, but maybe?" 

"Want to head back to the work room and try to make one? Do you have any sort of oil we could put on it?"

"I have lamp oil but that's flammable and we shouldn't get it too hot. I guess there's...butter?" 

"Yeah, or soap or something. Butter goes in things that get cooked, it can't do anything too awful when it gets hot."

"Guess we can try butter and soap and see which works better. I don't think soap is flammable although I have to admit I've never tried." She starts trooping back towards her workshop. 

They can stop by the dining hall on the way and get some butter. On bread, because that's the easiest way to carry it and also reduces the odds of someone looking at them funny.

And Sandra grabs some saddle-soap from the Companions' stable on the walk back. "All right, what should we make the stopper of? I think if we make it glass, it could be really slidey." 

"Yeah, glass seems like the best way to get it fitting really perfectly in the tube. How about I make the big jar and then you do the fiddly sizing bit?"

"Sure." Sandra sits back to watch him work, humming to herself and absently sticking her finger in the butter pat on their piece of bread. 

He heats and pushes and pulls and Fetches and eventually he has a slightly lopsided tank with a tall neck that's as symmetrical as he can make it, with a narrower bit where the neck meets the tank so the stopper can't completely fall in.

Sandra looks impressed. "You're so fast at that." She stares hard at the neck and tweaks it to make it even more perfectly symmetrical, then, with intense focus, starts working on a stopper perfectly shaped to fit it. 

"And you're impressively precise! It's very convenient that we're good at different things." (The thing she's good at is reflective of actual skills and the thing he's good at is pure luck, but it's still nice that they have one of each.)

Sandra checks the cork for fit - it's pretty good - and then carefully butters it, wiping away a few breadcrumbs that stuck on. She attempts sliding it in. 

It slides pretty well. Stops a ways down the neck, but well before the pinch-point, apparently held up by the pressure of the air inside. 

Bruce takes a moment to look at it. "Huh. It's cool to see air doing something. I mean, wind does things, but--I don't know, I just think it's neat. Anyway, uh, shall I heat it up?" He wraps a bit of wire around where the top of the cork currently is, so it will be obvious if it moves.

"It's so neat!" She's looking at their setup with something like awe. "Sure, heat it up and see what happens. Um, slowly, I don't want you to break it or shoot the cork out the top." 

Nod nod. "I'll be careful." He heats the air slowly, doing it directly rather than using a weather-barrier for greater precision and in case cooling the air outside the container would interfere somehow.

The stopper moves up the neck. A bit in fits and starts, it's not perfectly lubricated.