Glass is used in many modern inventions such as tableware, windows, lenses in telescopes and many more things. Before the modern times, people found glass, instead of making it.  Natural glass is sand that was hit by lightning.  Volcanos erupting and lava touching the sand on the shore led to obsidian, a black glass like material which was mostly used in tools, jewelry and pottery, but sometimes in clothing.   During the height of the Roman Empire, glass making was an efficient and popular industry.  Glass had to be kept a certain temperature or it would turn an unattractive yellowish-green that is not very nice looking. Glass makers perfected the art of clear glass. known as Forest Glass. Forest glass could be many colors such red, blue and green.  There was high demand for quality glass products in other countries, so glass was a major export, boosting trade.  After the collapse of Rome, people knew and understood how to make glass, but didn’t have the complex and expensive tools to make it. So, glass making died down rapidly until almost no one made glass. I hope you gathered some important information on glass.