The main ingredients used in making glass bottles are sand soda ash, limestone, and cullet. Sand is by far the most important raw material as it provides the foundation of the container. It is what determines the hardness and the durability of the bottle. Silica, a component of sand, makes up about 70% of the glass bottle, and it affects the melting point of the final product. More silica means a high melting point and vice-versa.