Think of washing soda as an 'energy catalyst' for glassmaking—just as salt lowers the freezing point of water to help melt ice on roads, washing soda lowers the melting point of sand to help create molten glass efficiently.

In the glass manufacturing process, a mixture of silica sand, limestone, and sodium carbonate is heated to high temperatures. Sodium carbonate ($Na_2CO_3$) reacts with silica to form sodium silicate ($Na_2SiO_3$), also known as 'water glass'. This reaction significantly reduces the melting temperature of the glass mixture from approximately $1700°C$ to around $1500°C$.

Always remember that 'washing soda' ($Na_2CO_3$) is distinct from 'baking soda' ($NaHCO_3$); the latter is used in food, while the former is for heavy industrial cleaning and manufacturing.