Science, Tech, Math › Science Colored Glass Chemistry: How Does It Work? Share Flipboard Email Print Mint Images/Tim Robbins / Getty Images Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate by Anne Marie Helmenstine, Ph.D. Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. Updated July 27, 2018 Early glass derived its color from impurities that were present when the glass was formed. For example, 'black bottle glass' was a dark brown or green glass, first produced in 17th Century England. This glass was dark due to the effects of the iron impurities in the sand used to make the glass and the sulfur from the smoke of the burning coal used to melt the glass. Man-made Glass Coloration In addition to natural impurities, glass is colored by purposely introducing minerals or purified metal salts (pigments). Examples of popular colored glasses include ruby glass (invented in 1679, using gold chloride) and uranium glass (invented in the 1830s, glass that glows in the dark, made using uranium oxide). Sometimes it is necessary to remove unwanted color caused by impurities to make clear glass or to prepare it for coloring. Decolorizers are used to precipitate out iron and sulfur compounds. Manganese dioxide and cerium oxide are common decolorizers. Special Effects Many special effects can be applied to glass to affect its color and overall appearance. Iridescent glass, sometimes called iris glass, is made by adding metallic compounds to the glass or by spraying the surface with stannous chloride or lead chloride and reheating it in a reducing atmosphere. Ancient glasses appear iridescent from the reflection of light off of many layers of weathering. Dichroic glass is an iridescent effect in which the glass appears to be different colors, depending on the angle from which it is viewed. This effect is caused by applying very thin layers of colloidal metals (e.g., gold or silver) to the glass. The thin layers are usually coated with clear glass to protect them from wear or oxidation. Glass Pigments Compounds Colors iron oxides greens, browns manganese oxides deep amber, amethyst, decolorizer cobalt oxide deep blue gold chloride ruby red selenium compounds reds carbon oxides amber/brown a mix of manganese, cobalt, iron black antimony oxides white uranium oxides yellow-green (glows!) sulfur compounds amber/brown copper compounds light blue, red tin compounds white lead with antimony yellow Continue Reading Stained Glass Windows: Medieval Art Form and Religious Meditation Gemstones On Fire? - Top 10 Gemstone Special Effects Get the Facts About the Element Manganese Get the Facts About the Element Selenium What Is Electroplating and How Does It Work? Understand the Tyndall Effect in Chemistry How to Distinguish Brown Minerals—Photo Gallery The Science Behind How Hair Coloring Works What Is Glass? - Composition and Properties All About Quartz, One of the Most Common Minerals on Earth Know the Table Salt Formula Understand What Activated Charcoal Is and How It Works OLED Technology and Who Invented It Some Interesting Facts About the Element Selenium Characteristics of the Most Common and Significant Black Minerals What is the Flame Test and How Do You Do It?