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.
Color chemistry
The following additives make the distinctive colors:
Selenium makes red; copper or gold, depending on the concentration, make ruby or cranberry; sulfur, carbon or iron salts make amber; uranium makes yellow green or vaseline; cadmium sulfide makes yellow; titanium makes yellow brown; iron oxide and chromium make dark green; iron oxide makes green blue; copper oxide makes turquoise; cobalt with potash makes blue; manganese makes purple or amethyst; nickel makes violet; nickel, depending on the concentration, makes black; fluorspar or zinc oxide make white glass, and tin oxide, arsenic and antimony make milk glass.
Glass of a different color
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, to protect the wine or beer from the light that could change its taste. Dark-colored wine bottles also hide the unsightly sediment that accumulates at the bottom.
Often used for powder jars or a bedroom vanity piece, 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, which 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 is a Venetian invention, the site of a longstanding history of glassblowing and glass works. Milk glass, which resembles porcelain, was commonly used at weddings for items such as bride baskets to hold money for the newlyweds.
Color reveals a great deal about the chemistry and history of collecting glass.
(Dr. Lori Verderame hosts antiques appraisal events worldwide and is the star appraiser on Discovery channel's TV show, Auction Kings. To learn about your antiques, visit www.DrLoriV.com, www.Facebook.com/DoctorLori, @DrLori on Twitter, and (888) 431-1010.)