I oftentimes ship a sauce only sold in my area to family at different elevations. The problem is that the bottle it’s sold in isn’t very secure and many times it’ll break in transit and leak everywhere.
What should I look for when shopping for bottles/containers to use for shipping?
Right, it’s just popping open on top where it connects to the flip top lid.
I’ve tried just throwing a plastic layer between the lid and the bottle (like Zip-Lock bags) but that didn’t help much.
I was thinking of using a glass airtight container or glass jar but I’m worried about it cracking in transit.
You just need to have as little air in the container as possible, it’s the air that expands as it good up in elevation. If it’s glass, fill it all the way. But plastic that you can squeeze all the air out of seems better if you can keep it sealed tight. Piece of tape over the flip top?
Why not just replace it with a cap that isn’t a flip-top? Screw it on tight, squeeze the bottle slightly before putting the cap on so there’s a slight negative pressure. That would be my first thing to try.