Roman glass objects have been recovered from domestic, industrial and funerary contexts across the expansive Empire. As in the modern day, glassware in antiquity was considered an art form, with the best pieces valued higher than wares made from precious metals. The iridescence on ancient Roman glass was unintentional, and was caused by weathering on its surface. The extent to which a glass object weathers depends mainly on the burial conditions; however, the humidity, heat, and type of soil in which the glass was buried also all affect its preservation.
To find out more about Roman glass please see our relevant blog post: Collecting Roman Glass.