Various solutions in small amounts are used along with the water - vinegar is one.
I heard a story some years back, when higher flying and faster aircraft were being developed, and had reached a point where there was a need for pressurized passenger compartments.
Conventional engineering wisdom at that point in time dictated that making passenger space airtight using conventional construction materials and techniques was "impossible"
The story continues, that the major aircraft maker next took new aircraft engineering students right off the graduation stage, hired them, and assigned them the task of development of a pressurized cabin, during which they were carefully kept apart from other factory engineers. They had never yet been exposed to the "fact" that what they had been assigned was "impossible" - and so, they went ahead and developed what was assigned to them - the "impossible"...
SO, yeah - ask your son - but if he's been out of school very long, and exposed to his peers - you can also expect the same "canned", textbook answer other such engineers quote - no disrespect intended...