Please choose the correct solution to the question: To make a concrete sphere.

Solution1: Take a spherical shell and spray with oil before pouring in the dry concrete into it. Allow to dry and set. Break the glass shell to remove the concrete sphere.

Solution2: Take a glass spherical shell and spray with oil before pouring in the mixed concrete into it. Allow to dry and set. Break the glass shell to remove the concrete sphere.

Answer format: solution1/solution2
Answer: solution2