I love that. It reminds me of the beautiful things my aunts had back in the 50's.

Greywings, thanks for reference to MSDS. I knew this sort of thing must exist out there somewhere, I just didn't know what it was called. There must have once been, or perhaps still are more than one dip-it as jannie's package contains no phosphorous and greywings link does. I have found links to two, perhaps different, coffee maker cleaners. One dip-id product contains, or did contain, citric acid and sulfamic acid which are, or once were the workhourses in denture cleaners.

Be very careful with a glass thermos interior. This glass is thin and fragile- easily broken. If you do use a brush, be gentle. A brush made with twisted wire is probably asking for trouble. A sharp rap or poke of the metal part may shatter the glass. For this reason, try chemical cleaning agents first. In addition to the hints in the above posts, try vinegar. (Vinegar has 4% acetic acid. This is the main cleaning agent). Vinegar is very good for disolving calcium and hard water deposits. Fill the thermos about 1/5 to 1/4 full of vinegar and then add warm to hot water until full. Do not cap and let sit for a couple of hours, and then pour it out and immediately rinse. Caution: Do not mix vinegar with amonia. Vinegar is an acid and amonia a base. These could react violently, and since they react with each other, a new compound is formed and the cleaning power of both are diminshed or neutralized.

rob333, this old fogey has discovered that no matter how many myths are busted, there's always more to come. I came back to add that I just tried something that truly surprised me. Was at my neighbor's and he was talking about the terlit buildup lately and it jogged my memory about a cleaner I saw endorsed by several people. Zep Acidic Toilet Bowl Cleaner. I had bought some and never got around to trying it so I went home and got it and we gave it a shot. Squirted it on, let it sit 5-10 min and gave it a quick brushing and I was really shocked. Half of the crusty buildup came off right away. Wasn't perfectly clean but I wonder if a sandblaster would still have crust on there. I left the bottle for him to give it another treatment in a day or two and see how it works. I don't remember where I read about it so I can't give credit but I'll be buying it from now on. I should also add that I did NOT scrub it either, just a brushing with a well-worn scratchbright pad type toilet bowl "brush". Didn't try it with the pumice stone but I'd venture a guess that pumice would help it too.