What acid should I use to break through an egg shell as a class demonstration?

Question

I would need it to degrade the shell within a 45 minute time period.

Answer 1

Acetic Acid...(Vinegar).

HCl even at 10% strength is risky. Stick to vinegar.

Answer 2

Acetic acid will take more than 45 minutes, I would try Hydrochloric acid that is about a 10% solution.  

Answer 3

i second that. vinegar.