I have recently done the eggshell experiment, exposing several eggshells to different beverages. What surprised me most is that, after 3 days of immersion in lemonade, the eggshell turned corrosive, this means, had lots of bumps on it. In fact, it gained weight... It would be very gratifying if you could answer why did the eggshell in lemonade turn corrosive and why did it gain weight. Thanks!
I believe eggshells are made of calcium carbonate, a weak base. Upon addition of any acid to a carbonate, CO2 and water are released and a salt of the acid and base is formed. It may be possible that the salt has deposited itself onto the the eggshell. It might be possible to dissolve that salt by adding surplus water.