So there I am in my shower this morning. What should be a
pleasant soothing experience turns out to be a very stressful
but educational event.  As the hot water sluices over me, I
allow my mind to wander on to nothing of importance. I'm
enjoying the delightful feel of being totally relaxed, warm and
fuzzy. Then I make the mistake of opening my eyes.  Right in my
line of vision is what appears to be dirty grungy grout. I look
up, down and around.  My beautiful white ceramic tiles are a
sickly gray with grayish black grout lines.  OK. Explain this to
me.  Water is clear. Soap is a cleaning agent. How can those two
things end up making my shower and bathtub look like the inside
of a coal mine?  Well, are you ready for your science lesson for
the day?  I've learned that water is a chemical substance. It's
formula is H2O. One molecule of water has two hydrogen atoms
covalently bonded to a single oxygen atom.  Now if you have hard
water, (my hand is raised) that means it has high mineral
content of calcium, magnesi