Eggshells in my coffee

OK, so this is a stupid thing, but I can't find an answer so I thought maybe someone else would know.

One morning a few weeks ago while cooking breakie, I dimly recalled this thing I'd heard once about throwing rinsed eggshells in the coffee grounds.

Figuring why not, I rinsed, crushed them in my hand, and dumped them into the ground coffee (drip flat filter). Mmmmmm. Noticeably better coffee. I've been doing it ever since and it's consistent.

Does anyone know the reason or rationale behind this ? I googled around but couldn't find anything other than a reference to campfire or cowboy coffee and well, placing eggshells and grounds in your compost (which I already do).

Any chem or food science majors care to enlighten me ? I know eggshells are mostly calcium carbonate (CaCO₃), but...

playing : Home (Feat. Phil Collins) by Bone Thugs n' Harmony

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