Just felt like I would like to share my experience as a new chicken raiser! I hear and read all about calcium in the chickens diet and about using the shells to feed back to the chickens. I found that, after the eggs have been in the 350 oven for 10 minutes, I let them cool and then, if you have a small electric coffee bean grinder, put the shells in that and give it a few quick pulses. In seconds, the shells are nicely ground into powder that is then added to their feed or offered separate. It works great!