COLORED GLASS CHEMISTRY - 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. 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. 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.

.................................................................................................................................................................

Colored Glass Chemistry

How Does It Work?

By Anne Marie Helmenstine, Ph.D.

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

Anne Marie Helmenstine, Ph.D.

Chemistry Expert

Education

Ph.D., Biomedical Sciences, University of Tennessee at Knoxville

B.A., Physics and Mathematics, Hastings College

Introduction

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/the-chemistry-of-colored-glass-602252