Ruby Glass Souvenir Cup

by Dr. Lori Verderame

Trying to identify and value colored glass pieces you bought thrifting? Colored glass–vintage or antique, modern or contemporary–is always a popular collectible item no matter what. While most glass is colorless or clear including soda lime glass, once metals or oxides are added to glass, colors appear and the whole world changes. Metals or oxides can be added to glass to change its look. The addition of metals or oxides to glass during the glass blowing, molding or machine production process can change glass for the better. Do you like the way glass catches the light and changes the look of a room? Here’s why colored glass is so popular and valuable in the antiques market.

First let’s learn which additives, metals or oxides that is, give glass its distinctive colors. There are many metals or oxides that are used in the production of colored glass. To make the colors of the rainbow, various additives are used such as selenium, copper, gold, carbon, iron salts, sulfur, uranium, cadmium sulfide, titanium, iron oxide, chromium, copper oxide, cobalt, potash, manganese, nickel, fluorspar, zinc oxide, tin oxide, arsenic, and antimony. There are many different additives used to give colored glass their distinctive colors.

Red Glass

Ruby Glass Souvenir Cup

Red glass is achieved when selenium is added. Ruby glass is the result when adding copper or gold to glass in a different concentration than cranberry glass. Red glass is some of the most popular glass for etching or cut glass designs since the bright red color gives a nice contrast to the clear or cut elements. Like ruby glass, cranberry glass is also red in color and has a similarly attractive quality when cut. In a manner similar to ruby glass, cranberry glass is achieved when copper or gold is added to glass in a different concentration than ruby glass.

Like glass of other colors like cobalt blue glass, ruby glass is associated with its impressive additive—gold. The use of gold in the glass making process to make ruby glass resulted in this type of red glass serving as a well known status symbol. People who had ruby glass in their homes were seen as the elite in culture. Many people collect ruby glass pieces and pay high prices for the rare ruby glass examples. Ruby glass is presented and made into famous ruby glass cut to clear vases, ruby glass bowls, drinking glasses and goblets, and many other types of glass forms. Ruby glass, with its gold additive, is often featured in objects such as decanter sets, goblets, and vases too.

Yellow, Orange, and Brown Glass

Amber glass emerges when sulfur, carbon, and iron salts are added to glass. Some of the most popular pieces of glass collected are amber glass pieces for its rich color and deep hue. Amber glass which has yellow and brown color is not unlike yellow-brown glass which results when titanium is added to glass. Yellow glass is the result of adding cadmium sulfide to glass and it is not as common but very popular with collectors.

Ever wonder why beer, wine, and liquor bottles are stored in brown glass when you try to identify and value colored glass?  The color of glass speaks volumes about its use. Glass design is based on many factors. For instance, bottles for liquor, wine, and beer bottles were typically brown or green in color in order to protect the wine, liquor, or beer from the light that could change its taste over time. If wine, liquor or beer are stored in a clear glass bottle, the contents could be altered by the light reacting with the liquid contents inside the bottle. Dark colored wine bottles which may be brown or sometimes green will also hide the unsightly sediments that accumulate at the bottom of a wine bottle as the liquid settles over time.

Uranium or Vaseline Glass

Vaseline Glass Bowl

It is the famous yellow or yellow green glass that is known as uranium glass or Vaseline glass that many collectors try to find. It is a treasure hunt for many to discover a good piece of uranium or Vaseline glass and to identify and value colored glass pieces like it. Uranium or Vaseline glass is achieved when uranium is added to glass. This type of glass is very popular and has been since it was discovered in the late 1790s. This type of glass fluoresces under black light. There are many types of glass thanks to the additives discussed above and these additives also allow certain types of glass to rise in popularity and collectability.

For instance, one of the most highly sought after types of glass for collectors is uranium glass, also known as Vaseline glass. Why do we call uranium glass also Vaseline glass? The amount of uranium oxide that is included in glass pieces ranges from trace levels to about 25%. Uranium was added to glass to give it a glowing or fluorescent look shortly after its discovery by a German chemist in the late 1780s. Uranium glass was first produced and marketed throughout England and the rest of Europe with great market success.

Today uranium glass is very desirable and ranges in value from $50 for small pieces into the several hundreds of dollars range for impressive forms of Vaseline glass. Vaseline glass is achieved when uranium is added to glass which is a type of glass that is very popular and fluoresces under black light. While a collecting boom in art glass has been going on since the 2000s, Vaseline glass fell out of favor in the late 1900s after uranium was needed for use in other industries. Today, collectors of uranium glass know that they had the inside track on the popular and valuable collectible glass type and look for select pieces in antiques malls, yard sales, online auctions, etc. Most uranium glass made today is used for jewelry pieces like beads or earrings.

Green and Blue Glass

Napoleon cobalt blue glass cup

Learn to identify and value colored glass like dark green glass by noticing its affect being achieved when iron oxide and chromium are added to glass. Green-blue glass is achieved when iron oxide is added to glass. Turquoise glass is the result when copper oxide is added to glass. Green glass was popular, the most popular in fact, glass during the production of Depression glass in the early 1900s. Green glass plates, cups, serving platters and other items are very collectible and emerge on the market often. In the mid 1900s, green glass was used in the production of crackle glass pitchers, vases, and other decorative items for the home.

Blue glass comes to be when glass is mixed with cobalt with potash. In many 19th and early 20th Century general stores, pharmacy and apothecary shops, blue or cobalt blue bottles lined the shelves filled with medicines, chemicals, and the like. Blue or cobalt blue glass bottles were made from a type of inexpensive glass. The blue or cobalt blue color had a two pronged approach: protection of the medicine from light like the green and brown glass bottles and marketing. The cobalt blue bottles’ color helped attract customers to new medicinal and healthcare products and newly introduced and innovative potions and tonics. The attractive of the colorful cobalt blue glass bottles quickly became synonymous with good health.

The modern glass makers of decorative glasswares like Murano or Blenko produced blue glass items for use in home decor which today are of great interest with collectors. For instance, American Blenko glass pieces –from vases to home decor bowls and more –dating from the mid to late 1900s can command values rising to the several hundreds of dollars for a specific piece. Fine Murano glass pieces from the glass blowing center of Venice, Italy have been popular in a striking cobalt blue color for centuries. With values rising into the several hundreds to thousands of dollars range for each hand blown piece, Murano glass remains a popular item with the international collectors. And the status associated with blue glass has been well known and dates back many centuries. It is often associated with various monarchs, historical figures, and others. Cobalt glass, like this cobalt glass for the Emperor Napoleon, is often times associated with the ruling classes in history.

Purple and Black Glass

When it comes to dark colored glass, many people look for, collect or resell purple, violet, indigo, or black glass. In various forms, purple glass is achieved when manganese is added to glass.
A variation on purple glass is amethyst glass. Amethyst glass is achieved when manganese is added to glass, also in a different concentration. In this same family of glass colors, violet glass is achieved when nickel is added to glass and so is black. Black glass, like violet glass, is the result when nickel is added to glass in a different concentration or chemical manner. The dark glass colors has been a good choice for decorative objects, vases, bowls, candlesticks, and cabinet plates. Amethyst glass can be very expensive to collect on the vintage and antique markets commanding several hundreds of dollars for a prime piece in a good looking form.

White and Milk Glass

Indiana Glass Goblets
White glass is achieved when fluorspar or zinc oxide are added to glass. Milk glass is the dense white glass that is achieved when tin oxide, arsenic, and antimony are added to glass. Milk glass was an Italian invention originating from Venice, Italy. In much of Europe, milk glass grew in popularity quickly and continue to attract collections because of its resemblance to expensive fired porcelain ceramics. Venice and its surrounding islands were the site of a long-standing glass blowing center that dates back many centuries in Murano. Milk glass was commonly used at weddings for items such as bride’s baskets to hold money or other gifts for the bride and groom, vases for flowers, compotes for chocolates and candies, and other bridal gifts. Milk glass was very popular in the 1940s-1960s and enjoyed a revival in the early decades of the 2000s. Milk glass is often enhanced with molded forms of grapes, leaves, or flowers within the body of a piece or decorated with figural elements like rabbits, foxes, or cherubs serving as finials or object forms.

Color says a lot about how a piece of glass was made. The many color variations of glass objects reveal a great deal about the long history of glass production as both collectible and functional objects.

Watch videos on my YouTube channel where I show you and talk about how to identify and value colored glass pieces that I’ve seen and appraised. I can appraise your glass pieces from photos or you can show me your pieces during a video call.