Usually when eggs are painted the insides are blown out. You make 1 small hole & then on other side little larger hole & blow insides out, seems like you break the yolk 1st!WASH well or they will smell! Suppose you could fill it with something so it wouldn't break but plaster of Paris would break & concrete would be awfully hard to get in that little hole so maybe a resin??? Then any sealant would work. My painted objects usually get Krylon Clear sprayed on them. I haven't painted any eggs.

Thanks, I hadn't thought about washing them after removing the egg from the shell. Seems so obvious now ;)

Anyone else with an idea?