One cute test later and I not know I can’t use upholstery vinyl for the bag: it leaks like crazy even though the seams are good.

a tiny uilleann pipe bag, about as tall as a ballpoint pen

This material was okay for the bellows, which is only under pressure for a moment as it fills the bag. Leakage here isn’t a big problem. Leakage in the bag would be a big problem.

So I’m back to exploring materials again. I’d like to avoid leather if possible: it’s tough to work with, and as a vegetarian for decades, a leather bag is going to invite distracting questions I’d rather not waste time answering.

Material Candidates

After some research, it seems like the candidates are:

Upholstery Vinyl with a liner

I could use a trash bag to line a vinyl bag. It’d be crinkly and might wear out quickly, but it would feel like leather (on the outside) and using an internal bladder means I wouldn’t need to worry about making an airtight seam in the fabric.

Ripstop Nylon

This is what kites are made of. I don’t think people are going to like the way it feels, although it would be incredibly lightweight.

TPU (Urethane) coated fabric

I think they make raincoats out of this? It might feel about right, and you make the seal with this special tape that you then iron to fix. That sounds like pretty easy construction.

DIY Packraft has instructions on how to use a “leather iron” to make airtight seals. If you can make inflatable rafts out of this material — rafts that prevent a human being from drowning — I reckon I can make a good bagpipe bag.

It even seems one type of fabric you can get TPU-coated is… ripstop nylon.

Neoprene

They make diving suits out of this. I don’t know a whole lot about neoprene: I think it’s airtight? I think it’s rubber? It might feel too stretchy.

Latex sheets

This is for sure rubber. It’d be pretty stiff, and wouldn’t feel quite right, but I don’t doubt I could get an airtight seal with latex. I also don’t doubt a lot of people would get contact allergies, but I guess that’s what the (cotton) bag cover is for.

Next steps

I’m going to try TPU-coated fabric. I think it will feel kind of similar to leather, and it seems like it might be easy to seam.

Using a bladder inside the vinyl has a certain appeal, though. I could then stitch the bag, which would look cool and handmade. So that might be the next thing I try, if TPU fabric doesn’t work out.