Colored Antique Glass - What Gave It Those Beautiful Hues?

  • 01 of 06

    Beginning with Glass Ingredients and Clear Glass

    Rare Steuben Clear Glass Candlesticks
    Rare Steuben Clear Glass Candlesticks, 10 1/2" tall, sold for $2,040 at Morphy Auctions in October, 2011. - Morphy Auctions

    Glass was made, whether pressed or mouth blown, with three primary ingredients: sand, soda (also referred to as potash), and lime. Uncolored glass is made similarly to colored glass. Metallic oxides such as lead are added to remove impurities yielding clear glass, according to The Charles Hosmer Morse Museum in Winter Park, Florida.

    When clear glass is referred to as “lead crystal,” this indicates that lead oxide was added to the glass during manufacture to improve the quality. Glass made in the...MORE early 1800s had flint added to it to improve clarity and durability. The term "flint glass" continues to be used to describe antique glass of good quality made through the early 1900s, even though lead replaced flint as a clarifying additive in the mid-1800s.

    Manganese was also used for clarifying glass through 1917. When this variety of clear glass sits in the sun for a long period, such as an insulator on a telegraph pole, it will turn various shades of purple.

    Continue to page 2 to learn about BLUE glass.

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  • 02 of 06

    How Blue Glass Got Its Color

    Cobalt Blue Flint Glass
    Cobalt blue flint glass lot, circa 1890s, sold for $420 at Morphy Auctions in October, 2011. - Morphy Auctions

    Blue antique glass was given its color by adding cobalt oxide to a molten glass mixture of sand, potash and lime. This additive accounts for deep blue glass being referred to as cobalt blue. Other shades of blue were achieved by lowering the amount of cobalt oxide added to the glass mixture.

    Continue to page 3 to learn about AMETHYST glass.

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  • 03 of 06

    How Amethyst Glass Got Its Color

    Set of Amethyst Glass Apothecary Jars
    Set of amethyst glass apothecary jars, possibly made by L.E. Smith, sold for $1,800 at Morhpy Auctions in October, 2011. - Morphy Auctions

    Amethyst, or purple, glass was given its color by adding manganese oxide to a molten glass mixture of sand, potash and lime.

    Amethyst glass should not be confused with clear antique glass that has changed color due to sun exposure. This type of clear glass was made with manganese as a clarifying agent, and the sun will turn it various shades of purple if enough time passes. When compared to the rich plum color of amethyst glass, it looks more violet in nature and is lighter in color.

    It's also...MORE wise to note that "sun purple" glass has been artificially produced by some unscrupulous sellers who expose antique clear glass pieces to ultraviolet light in order to change the color in an effort to make it more desirable.

    Continue to page 4 to learn about GREEN glass.

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  • 04 of 06

    How Green Glass Got Its Color

    Olive Green Demijohn Bottle
    Olive green onion-type demijohn bottle, circa 1850, 16 1/2" tall, sold for $570 at Morphy Auctions in October, 2011. - Morphy Auctions

    Green antique glass was given its color by adding iron oxide to a molten glass mixture of sand, potash and lime. Varying shades of green ranging from light to dark with an olive hue, were achieved by lowering the amount of iron oxide added to the glass mixture.

    This type of glass should not be confused with green Depression glass containing uranium oxide, or vaseline glass, which is more yellow in color and will also fluoresce under ultraviolet light due to uranium content.

    Continue to page 5 to...MORE learn about BROWN glass.

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  • 05 of 06

    How Brown & Amber Glass Got Its Color

    Brown Antique Milk Bottles
    Lot of two brown glass milk bottles sold at Morphy Auctions for $120 in October, 2011. - Morphy Auctions

    Amber and brown antique glass were given their color by adding iron/sulfur oxide to a molten glass mixture of sand, potash and lime.

    Continue to page 6 to learn about BROWN glass.

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  • 06 of 06

    How Red Glass Got Its Color

    Ruby Red and Cranberry Glass Examples
    Mary Gregory ruby glass mug, cranberry bullseye sugar shaker and a ruby flash frosted tumbler sold as a lot for $60 at Morphy Auctions in October, 2011. - Morphy Auctions

    Red antique glass was given its color by adding gold oxide to a molten glass mixture of sand, potash and lime. More in the mix gold would result in deep red like the Mary Gregory style mug shown here. Other shades of red and pink, like that of the cranberry glass shaker depicted here, were achieved by lowering the amount of gold oxide added to the glass mixture.

    The other item shown here (at right) is clear frosted glass with painted red accents, also known as "flash" coloring in the...MORE antiques business, rather than ruby glass.