Cobalt glass is any glass that has been combined with small amounts of copper and cobalt to produce a blue appearance. Cobalt glass has been discovered in ancient Babylonian sites, but it was not produced commercially until the late 1800s. Although cobalt glass is available anywhere that sells glassware, the antique cobalt blue glassware is far more valuable. Many people like to collect the antique cobalt glass for its value, while others simply prefer the look of contemporary cobalt glass on their tables.
Look for any type of glassware, vase, flask or jar that has a blue appearance. These are all considered to be cobalt glass. Some glass will be entirely blue, while other pieces may have a striated blue appearance. It is also common for the glass to have white swirled along with the blue.
Examine the saturation of the blue color within the glass. There are three basic shades of cobalt glass. The lightest shade is called cornflower blue and appears as a light blue, almost transparent color. The medium color of cobalt is a true blue color. The darkest cobalt glass is called deep cobalt and has a slight purple tinge.
Determine if the cobalt glass is antique or modern. Compare the cobalt glass that you have with collectors' references to determine the value of the glass. One such reference is provided in the Resources section.