By Rebecca Ruger
Old Coke Bottles, Ball canning jars, vintage baking soda jars, and ink bottles made during the late 1800s in the United States and up until the first few decades of the 20th century were often light green, or sea foam glass. However, glass experts do not use sea foam as a formal color name; the soft and soothing pale green that beachcombers know as sea foam would have been called aqua or aquamarine, and they would have attributed a modifying descriptive term to describe any of the shades of aqua, i.e., blue aqua, green or greenish aqua, pale blue aqua, etc.
Curiously, most of the "sea foam" glass that we know was not specifically or purposefully colored; it is a result of too much iron in the sand that was used to make the glass. The sea foam sea glass, therefore, would be one of the so called "natural" colors, those that result naturally from the basic ingredients in a glass batch. In general, with lesser amounts of iron or less oxidation of that iron, shades of bluish to greenish aqua are achieved. With higher amounts of iron or higher oxidation of the iron, darker greens will usually occur. Additionally, other factors may have played a role in the depth of the natural greenish hue achieved in glassmaking.
Julian Toulouse, author of A Collector’s Manual—Fruit Jars (1969) explains, “A reducing flame, or one with less oxygen supplied for burning, might produce a bluish-green because the iron in the sand might then be reduced to one of the bluer iron oxides—an excess of air might make the oxidized green iron oxides predominate. Early glassmakers knew little about this. Thus a fire banked for the night and with the air intake flues closed down, could produce quite blue glass for the morning’s start, and change slowly during the day when the air vents were opened wide for a hotter flame.”
Aqua glass, in all its variations of hue, was very common in all types of glass made in America prior to 1920. Colorless glass (now white sea glass) then began to replace the overused aqua as a bottling choice for manufacturers who wanted their product to stand out. With the notable exception of the iconic Coca-Cola bottle (which kept the light green color but changed its design to the well loved "hobble-skirted" classic to attract its own attention), most vintage sea foam glass found today will have been made before WWI.
On the rarity chart, sea foam is found in the common section, but certainly it is not a very common piece. The muted, calming colors of all the sea foam shades make it a collector favorite, and in general, the older the piece, the more value (even if only personal) the avid collector might attach to their glass.
This article appeared in the Glassing Magazine July 2017 issue.