Between Nature and Art: Transparent Streams of a New Liquid

Glass, a product of human invention, became synonymous with transparency early in the Roman imperial era and remained so throughout the Middle Ages sharing this quality with natural rock crystal. The present study, far from being systematic, develops ‘in streams’, like those of molten glass, so as better to illustrate the nature of this material and the ways in which it was used and appreciated in the Roman and post-Roman world – whether in objects of daily use or as expressions of theological, philosophical and scientific thought. The first part of this study will deal with physical characteristics of glass as a synonym for transparency. Secondly, I will analize how colored glass could perform as a visual and metaphorical filter to the outside world and could improve, alter or actually obstruct visual perception, thereby inspiring introversion and a reflective attitude. A perusal of the philosophical and thological texts of late Antiquity and the Middle Ages reveals how glass, and stained-glass windows, became perfect metaphors for theological concepts of great importance to Christianity West and East. Finally, I will show how the colored and translucent (not always transparent) glass used to fill windows between late Antiquity and the Middle Ages contributed to the definition of a sacred Christian space. From Carolingian times inwards, windows began to represent figures of proph