Thus, heating water does not cause calcium carbonate to precipitate per se. However, there is an equilibrium between dissolved calcium bicarbonate and dissolved calcium carbonate:
Ca2+ + 2HCO3- ⇋ Ca2+ + CO32- + CO2 + H2O
Confession: I just skimmed the first paragraph too.
And mould. I'm scared of mould too.
When we first moved into our rental and had our initial inspection, the caretaker (Len Parker, a chatty Irishman) gave me very specific instructions to buy a squeegee and make sure I "keep an eye on the limscale" in the bathroom. He then went on to talk about reducing condensation, and "always cover pots with boiling water" and "open windows to allow air flow" to prevent mould growth. But in England, they don't say it's "mould growth", they call it "Damp", like some kind of comic-book villain. Example: "you have to watch out, you might get Damp in the corners". Watch out - he's lurking behind the couch!
The University Accommodation Service even gives you handouts on reducing condensation. This was necessary, because my education completely failed me and I had no real idea what condensation was and really, where does the water on the window come from??? It's just in the air? As IF!! Magic??
I had never heard of mould-growth on walls or window sills. Living in Alberta, aka driest place ever, it's just not an issue. Getting static-electricity shocks every time you walk on your carpet in socks? Yes. Needing to use a dryer sheet to stop your clothes static-ing together? Yes. Mould growth? No.
Basically, in my jet lagged & post-international-move state of mind, Len Parker freaked the crap out of me. Ever since, I have been totally aware of the condensation on our windows, and wipe them down right away. I also religiously clean our bathroom. On more than one occasion I have google-imaged "mould on windowsills", and "limescale bathroom" to see if I'm doing okay. Here are the freaky images you get:
Exhibit A: Mould
So when we had our inspection to renew our lease, I was a little bit worried that Len was going to come in, and suddenly see the beginnings of mould growth, or chalky limescale developing in places I didn't know to look or clean. The night before I had that feeling you get before an exam - like this inspection was going to be an examination of my ability to properly care for a home and family. Seriously, renting is stressful!!
I am so proud to tell you that not only did we pass our inspection, but Len Parker actually clapped me on the back and gave me a side hug when he saw my bathroom. He said, (say it with an Irish accent, it's so much better that way) "Georgina! It's beautiful! Well done! It looks perfect!" You know what? I felt like the Best Housekeeper Ever.
Bathroom when we moved in:
Limescale? Pfffft. I'm not scared of you anymore. Well, maybe a little bit.