Gosh, I know this thread is old, but someone piqued my geek and when a geek is piqued you can't stop the information. Full disclosure, I'm not a chemist but I played one in college
When most people say "salt" they mean sodium chloride (NaCl). But "salt" is like the word "theory" in that the informal way people use it is actually different from its accurate meaning.
In essence, a salt is a positively charged [+] metal that ionically bonds with a negatively charged [-] nonmetal to form an ionic bond. Very loose example: Take an element from the left side of the periodic table (the [+] metals) and combine it with an element on the right side of the periodic table (the [-] nonmetals) and you form a salt.
Take a gander if you like: Dynamic Periodic Table
lithium + sulfur = lithium sulfide = LiS = salt
potassium + chlorine = potassium chloride = KCl = salt
calcium + bromine = calcium bromide = CaBr2
sodium + chlorine = sodium chloride = NaCl = salt
magnesium + sulfate (SO4
) = magnesium sulfate = MgSO4
is an anionic (another word for "negative ion") polyatomic compound. I know I said you take one [+] from the left and one [-] from the right and you have a salt. This is where we depart into more chemistry.
But I hope you get the idea that there is more to words than we give them credit for. And never ask a chemist to please pass the salt in a lab because you won't want to sprinkle what you get on your fries.
When you put salts into your hair, the higher concentration of them encourages cellular water to leave via diffusion* the hair and travel towards the salt in order to balance out the concentration. That's what causes cells to dry (through a process called osmosis) because of high salt content--it's why you're thirsty after eating salty food. But rest easy: because of those same "water enticing" characteristics, common salts are easy to wash out. Then simply rehydrate your hair once the salts are gone. If the occasional beach hair works out for you because perhaps the salts are "exfoliating" your hair, that's great. Just don't go putting salt in your hair on purpose on a regular basis, and definitely don't leave it in to dry.
*Here is some more reading, which clarifies even more that the salt is removing water not through osmosis (because hair is dead skin cells, not living water-filled skin cells): http://www.newton.dep.anl.gov/askasc...6/gen06003.htm
When he says capillary action, it's a wick-like effect. Have you ever seen a blood sample taken by a very narrow tube? Prick your finger and put the "capillary tube" at the blood and the blood is sucked into the tube without even trying, that is capillary action. So water is removed from your hair by simple physics, not osmosis (which is a form of diffusion) as in the case of a living cell.