Good Life

Art & Antiques | Colors of glass reveal chemistry, history

Why are wine bottles green? Why are beer bottles brown? Why are medicine bottles blue?

The answers to these questions speak volumes about American culture and design. For instance, bottles for wine and beer were typically dark in color, such as green or brown, in order to protect the wine or beer from the light, which could change its taste. Dark-colored wine bottles also hide the unsightly sediment that accumulates at the bottom of a wine bottle.

Often used for powder jars and bedroom vanity pieces, purple or amethyst glass has a long history. Purple or amethyst glass was first used in ancient Egypt and is a popular collectible today.

In many 19th century and early 20th century general stores and early pharmacy or apothecary shops, blue bottles lined the shelves.

Blue bottle glass was inexpensive to make and was of interest to those who were trying to attract customers to new potions, tonics and medicinal products. The cobalt blue bottles were attractive and became connected with signs of good health.

Ruby glass is associated with its additive, gold, making the collecting of ruby glass a high-society status symbol. Ruby glass is often featured in objects such as decanter sets, goblets and vases.

Milk glass was a Venetian invention, the site of a longstanding history of glassblowing and glass works. Milk glass was commonly used at weddings for items such as bride’s baskets, to hold money for the newlyweds, because milk glass resembled porcelain.

Color reveals a great deal about the chemistry and history of collecting glass.

Soda lime glass is basically colorless. Metals and oxides can be added to glass to change its color during the glass blowing, molding or machine production process.

The following additives make the distinctive colors:

• Red glass: selenium

• Ruby/cranberry glass: copper or gold, depending on the concentration

• Amber glass: sulfur, carbon, iron salts

• Yellow-green or vaseline glass: uranium

• Yellow glass: cadmium sulfide

• Yellow-brown glass: titanium

• Dark green glass: iron oxide and chromium

• Green-blue glass: iron oxide

• Turquoise glass: copper oxide

• Blue glass: cobalt with potash

• Purple or amethyst glass: manganese

• Violet glass: nickel

• Black glass: nickel, depending on the concentration

• White glass: fluorspar or zinc oxide

• Milk glass: tin oxide, arsenic, antimony