How far up do you fill the molds prior to freezing? Do you go right to the top or leave some room for expansion?
Filling the molds before freezing: Fill just over half full with water, when you set in the lid/inner mold, it will displace the water pushing it up to about 1″ from the very top. I like a little shorter fill, about 2″ from the top for a nICE cocktail glass.
Oh, and for clear ice: folks are getting clear nICE mugs by insulating the sides and bottom of nICE mug molds: wool sock, beanie, bubble wrap, and packing the mold in a snow bank. The top down freeze. Please send a pic as you evolve,