On 05/17/2021 01:00 PM, TimR wrote:
On Monday, May 17, 2021 at 1:31:30 PM UTC-4, Na'ilah wrote:
Thanks, TimR. Pretty sure drywall mud, etc. would not cling to a vertical pipe...

Are you saying lime scale would not be that thick or easy to scrape? What would you expect with lime scale? (This stuff was the texture of frosting mixed with sawdust.)

Also, maybe it's possible wax from the ring may have been in the mix, but it didn't look waxy/greasy/shiny at all.
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Have you ever tried to scrub lime scale out of the inside of a teapot? It's almost as hard as the metal. You might dissolve it with something acidic but abrasive pads don't even dent it.

For a teapot vinegar does a decent job. For a toilet I would go straight
to hydrochloric. My water is very hard and the toilet bowl cleaners that
contain hydrochloric acid get the job done.

That said, I've never seen a lime buildup like the OP described.