Smalt: An under-recognized pigment commonly used in historical period China

Smalt is a ground blue pigment made of potassium glass whose color comes from a small amount of cobalt oxide added during its preparation. It was very frequently used during the 15th to 19th centuries in Europe, but has by contrast been rarely mentioned or studied by Chinese researchers, despite having been identified in recent years on many Chinese antiques. This paper discusses analytical results from a selection of twenty-one samples of smalt, including wall paintings, architectural polychromy, polychrome sculptures, cave murals and textile paintings, each of which has been subject to a combination of polarized light microscopy, Raman spectroscopy and scanning electronic microscopy. This paper discusses the smalt’s identification, as well as its historical uses and trade.