Fabrizio Versus the Fluorescent World: glass
Glass Under Ultraviolet Light
Glass may look similar to the naked eye, but under UV light it might reveal completely different behaviors. In this episode of Fabrizio Versus the Fluorescent World, we explore how different types of glass behave under UV light—and why some glow while others remain completely dark.
Table of Contents
Optical glass
We begin with a fundamental reference: pure optical glass. The lens of the Fabrizio UV lamp itself is made of BK7 optical glass, a highly refined material used in precision optics. Thanks to its purity and controlled composition, it shows no UV fluorescence at all. This provides a crucial baseline for observation: pure glass does not fluoresce. Any visible emission under UV light is therefore the result of specific elements or compounds added during production.
Manganese glass
Things become more interesting when additives are introduced into the glass matrix.
The first example is manganese glass. Manganese has historically been added to glass to counteract the green tint caused by iron impurities, producing a clearer and more visually neutral material. Even when the glass appears blue—due to the presence of cobalt as a colorant—the manganese component remains detectable. Under UV light, manganese glass reveals a pale green fluorescence, typically weak but clearly distinguishable. This subtle emission is often uneven and can vary depending on composition and aging, making it a useful diagnostic feature for identifying this type of glass.
Uranium glass
Next, we examine uranium glass, one of the most iconic fluorescent materials. Widely used during the mid-20th century, it was popular for producing decorative objects with a characteristic yellow-green appearance, often referred to as opaline glass. This material contains uranium compounds and even exhibits measurable radioactivity. When exposed to UV light, uranium glass produces a bright, intense neon green fluorescence, which is immediate and unmistakable. Its strong response makes it one of the easiest materials to identify using UV examination.
Cadmium glass
Finally, we consider cadmium glass. By adding cadmium—often in combination with selenium—glassmakers were able to achieve vivid colors ranging from yellow to deep red and orange. Under UV illumination, cadmium glass displays a strong orange fluorescence, clearly distinct from the green emission of uranium glass. This fluorescence is typically very intense and uniform, making cadmium-containing glass easy to recognize.
Learn Technical Photography for Art Examination
Technical Photography is one of the most powerful—and often overlooked—tools for the scientific examination of art and archaeology. If you are a conservator, scientist, or art collector and you are not yet familiar with this method, it is truly a missed opportunity. Using simple, affordable equipment and a clear methodology, Technical Photography allows you to reveal underdrawings, retouchings, material differences, and conservation issues in a completely non-invasive way. Far from being complex or inaccessible, it is an easy entry point into scientific analysis. In many cases, Technical Photography represents the first essential step toward a deeper understanding of artworks and archaeological objects.
Scientific Art Examination – Resources:
Getty Conservation Institute (GCI) – USA
The British Museum – Scientific Research Department – UK
Scientific Research Department – The Metropolitan Museum of Art, New York, USA
C2RMF (Centre de Recherche et de Restauration des Musées de France) – France
Rijksmuseum – Science Department – Netherlands
