VIEW LARGER

Artist: John Northwood I
Title: Milton Vase, 1878

English, 1836-1902
Gift of Rebecca W. Hitt in Memory of Billy Hitt and Museum purchase

COBALTCobalt
CoO
Color

Cobalt oxide (CoO) is the strongest coloring agent. Even small quantities of cobalt oxide give glass a brilliant shade of blue, as in this English cameo vase.

In the ancient world, cameos were carved from shells or gemstones such as onyx and agate. The Romans developed a way to imitate these materials by using two layers of different colored glass. The technique was lost, however, until glassmakers in 19th-century England rediscovered the process.

Unlike the Romans, however, John Northwood I and his contemporaries applied hydrofluoric acid (HF) to the vessels to partially remove the outer layer of white and reveal the color beneath. Grinding wheels and pointed metal styluses were used to finish the design.