"Maybe if you had a really lightweight container and filled it with really hot air it would float up enough to pull you up with it?"

"....Whoa. What an idea. I guess we could try to test it, with a weather barrier or a heat-spell inside a container. Hmm, what's light, glass is definitely too heavy and metal is worse..." 

"Cloth? You could paint it so the air didn't leak through."

"Maybe! Or wax, or whatever it is they put on oilcloth that makes it waterproof, I don't think it'd make it that much heavier. Let's try to make something! How big, do you think - it'd probably work better if it were bigger, because then it'd be relatively less cloth compared to hot air inside." 

"And the more total air the more it can lift, probably. Maybe if we make one as big across as you are tall and see if that's big enough to lift the cloth? And then if that works we can get more and make it bigger."

"That's a lot of cloth! We'll have to make a special trip to the market or something. ...Er, how much money do you have, I don't think I can afford that unless I ask Savil for more supplies-money."

"I haven't really bad anything to spend my pay on but I haven't been getting any for that long either. We can make a really small one out of a spare bedsheet or something first, if we're careful not to cut it we can reuse it for part of a bigger one."

"Sure. Do you have a spare bedsheet or should I go hunt around Savil's suite?" 

"I've got one." Which is good, because this was his idea and he's the one who ought to be inconvenienced if they tear it or set it on fire or something.

He goes off and comes back with it. "We might end up wanting to sew it into a cylinder and then sew the ends shut; I don't see another way to do it that doesn't waste a lot of the space inside."

"Mmm, makes sense. Are you any good at sewing?" 

"I can't make it look nice but I've sewn up rips in my clothes and stuff."

"Well, I hate sewing, so if you don't mind...? I don't reckon it has to be pretty." 

"Sure." He can fold it in half and sew the edges shut. It takes a while but eventually he has a bag of air. It's not airtight, but if he leaves a little hole at one end he can fill it with air and then pinch it shut and it stays puffed up for a while.

"Figure it's worth testing heating the air and seeing if it feels less heavy, or floats up? Or should we wait until we've made it waterproof?" 

"Let's try it first." He'll feel better about getting wax all over it in addition to the more easily removable stitches if he has more evidence it'll work, and also he's excited. He heats up the air in the bag, slowly enough that he won't set it on fire.

The air tries harder to hiss out through the spot he's pinching, and in between the stitches down the side and at the other end. 

It does maybe bob up a bit? 

"I think it'll work! If I go back over the seams and do a better job, anyway."

"Neat! I'm excited. And then we can try waxing it, I think I can borrow the saddle wax from the stables..." 

"Good idea." Sew sew sew he is absolutely garbage at this but if he folds over a bit of cloth at the end and does multiple rows of stitches on top of but offset from each other it will be hard for the air to get out.

And Sandra goes off to get the saddle-wax; this takes her a while and he's finishing up by the time she's back. 

"Hmm - I need to go soon, but figured maybe we could try waxing just a bit of it now, to check how well it works or if we need something else?" 

"Yeah--and before that we should check how it handles heat; we don't want it melting everywhere or even worse, catching fire." If she assents, he tries putting a blob of the stuff in the lid of the can and heating it.

It melts! It takes less effort than boiling water does, even. 

Eventually it smokes a bit at the edges, but doesn't quite catch fire. 

"Hmm. I don't want to limit how how we can go too much. Maybe I'll just put it on the seams where it's needed the most and then if it melts it won't get quite as everywhere."

"Sure, that sounds good." Sandra watches him work, helping him spread out the melted wax-goo on the seems once it's ready. 

And then they can try heating it again!

"I think it's definitely lighter this time."