[palata]

> FWIW, I once went through an airport in my travels that took an infrared spectra of everyone’s water! They never said that, I recognized the equipment. I forget where, I was just impressed that the process was scientifically rigorous. That would immediately identify anything weird that was passed off as water.

Something like 10 years ago, I had my water checked in a specialised "bottle of water checker" equipment in Japan. I had to put my bottle there, it took a second and that was it. I have been wondering why this isn't more common ever since :-).

No idea if it was an "infrared spectra machine" of course.

[regularfry]

Cynically, it's so they can sell you another bottle on the secure side. If they spend money to give themselves a working mechanism to distinguish water from not-water, they lose the ability to create retail demand.

[palata]

I understand the idea, but it's not completely true: I empty my bottle before the security check, and fill it after in a fountain.

[regularfry]

Then you have successfully circumnavigated a problem that more forgetful people will run into head-first. It doesn't have to catch everyone for the shops who are tenants on the secure side to complain about lost sales.