It shouldn't matter,except for their taste preferences. I find if its not totally dry it doesn't grind as well. I have an old Mr coffee coffee bean grinder which gets it very fine,kind of a sandy powder texture. If you use a rolling pin on the broken pieces in a sealed bag & then use a mortar & pestle it gets pretty powdery also. The blender & food processor don't seem to grind it as finely.

Hi Eclaire!  You still have to put what the recipe calls for or what the recipe says.  One teaspoon ground eggshell is one teaspoon eggshell whether it is finely ground or coarsely ground.  I have used finely ground and coursely ground in my recipes before and it doesn't seem to make a difference in my cats' acceptance of their home-made.

Hi all,

understood, so no matter is finely or coarsly, it make no difference to become 1tsp. Firstly i thought it will be different not in term of taste or texture, it will be different that finely mean more eggshell and coarsly mean less eggshell added and hence the 1tsp may not be same to 1800mg or etc. thanks alot everyone.