[whzdm]

Why is hard water so drying on skin and on the hair?

I feel like this is a monumentally easy question but I cant think of an answer except well...

Hard water is "hard" because of the presence of Calcium and Magnesium ions as well as Calcium Sulphate.

Calcium Sulphate is a dessicant, so I am thinking any deposits on the skin or hair will dry them out...

 

[James]

Isn't hard water just an isotope of H2O, so why would there be any Calcium and Magnesium ions and Calcium Sulphate in it.

[jdurg]

Isn't hard water just an isotope of H2O, so why would there be any Calcium and Magnesium ions and Calcium Sulphate in it.

Absolutely not.  You're confusing hard water with heavy water.  (Heavy water is water made up of Deuterium atoms instead of Protium atoms).  As for the original hard water question, the reason why it makes your hair and skin feel dry is that the positively charged ions in the hard water get attracted to your skin and hair like a magnet.  This causes them to coat your scalp and hair which drys it out.  This buildup then flakes off as dandruff while causing your skin to be extra dry.

[movies]

In the chemistry dept. at my undergrad school there was an advertisement on one of the bulletin boards for some supposed special mosturizing water spray for your skin.  It was really very well marketed.  In turned out that it was just D₂O.

[Tetrahedrite]

Calcium Sulphate is a dessicant, so I am thinking any deposits on the skin or hair will dry them out...

 

Just for clarification:
CaSO4 is only a dessicant when it is anhydrous (the mineral is actually called anhydrite!) Hydrated calcium sulfate (gypsum or bassinite) are the hydrated forms  and are the types that would likely ppte out of solution. These minerals are not likely to act as a dessicant.

[whzdm]

Thanks guys