I live in Massachusetts, my house has 3 bathrooms and I live alone. If I don't scrub my toilet bowls once a week they build up brownish-yellow mineral stains. These seem independent of whether I've actually used that toilet bowl since the previous cleaning (since I live alone some toilets are seldom used).
Looking on the web there's lots of advice from "folksy" sources like "frugal blonde" or "professional mom" about how to clean toilets - usually involving vinegar, Clorox, pumice-sponges, etc, and lots of elbow grease, rubber gloves, bathroom fans and time. One guy uses WD-40! But being "folksy" none of these involve any discussion of the chemistry.
I thought if I understood the science I could save work and maybe even prevent the stains but I can't find ANYTHING on the web about this! What are the minerals in my water and what form are they in? Are they ionized or just some sort of suspension? What are the principal forms - I assume calcium, magnesium (and silicate?) compounds - and what form do they precipitate out in on the porcelain? What IS porcelain (chemically-speaking) anyway, and what makes such tight bonds at the interface between the minerals from the water and the porcelain surface?
If I knew the answers to these maybe I could even prevent these porcelain-mineral bonds from forming