1. ** Composition difference: **

- ** Lead-free crystal glass: ** The main ingredients are silicon dioxide, sodium oxide, calcium oxide, lead oxide (in small amounts or lead-free here). In the manufacturing process of lead-free crystal glass, other metal oxides are usually used to replace lead in order to reduce the pollution of drinks.

- ** Calcium sodium glass: ** The main components are silica, sodium oxide and calcium oxide. This type of glass does not contain lead, but it does not have other metal oxides in its composition to replace lead, so it is usually not called crystal glass.

2. ** Refractive index and optical properties: **

** Lead-free crystal glass: ** has a high refractive index, so it can better show the transparency and luster of the glass. This gives the drink a clearer color in the glass.

Calcium sodium glass: ** low refractive index, compared with crystal glass, its optical properties may be slightly ordinary.

3. ** Manufacturing process and use: **

- ** Lead-free crystal glass: ** The manufacturing process is relatively precise, usually used to manufacture high-end wine glasses, vases, etc., emphasizing artistry and quality.

Calcium sodium glass: ** The manufacture is relatively simple, widely used, including ordinary beverage cups, utensils, etc. This type of glass is generally more suitable for everyday use, and the cost is relatively low.