The first primitive glass

The earliest kind of glass was actually glazes for ceramic vessels. The earliest glass appears to have been produced in Mesopotamia around 4-5000 BC, but the production of glazes might be even older.

In this early process, people succeeded in separating the components of clay that melt when heated to yield glaze, and thus early glass could be produced. The oldest examples are from around 2500 BC in Mesopotamia.