Discoveries have been made of lead-glazed ceramic beads dating to the Warring States period (481-221BC), but lead-glazed vessels were first developed during the Western Han dynasty (206BC-9AD). Commonly known as Han lu (literally "Han green"), this is the first "true" glaze in China, and could actually come in a range of hues ranging from olive to emerald green due to the presence of copper in the glaze formula, or from amber to deep brown due to the presence of iron. Rare pieces of high quality can incorporate both colors, a precursor to the famous Sancai ("three-color") wares of the Tang dynasty (618-907AD).
The clay body is usually pink in color, and relatively course in texture, as it was not deemed necessary to wash the clay of sand since lead-glaze pieces were generally used for accompaniment in burial. Figurines were made in moulds, while vessels of circular section were sometimes thrown on the potter’s wheel. The pieces were then covered in glaze before being fired to a temperature of about 900*C. Glaze tends to be thinner and therefore less lustrous on Western Han pieces. By the Eastern Han period (25-220AD), lead-glaze ware could be found in tombs all over China from Inner Mongolia in the north to Sichuan in the southwest. A vast repertoire included vessels such as ewers, flasks and lidded tripods based on bronze precedents, models of vessels in common use such as ear-cups, bowls, ladles, censers, and trays, and representations of things from everyday life: tables, lamps, candlesticks, ovens, grinding mills, pestle-and-mortars, ponds filled with fish, pigsties, grain silos, courtyards, houses, towers, and domestic animals (pigs, dogs, horses, ducks, chickens, goats, etc.). Some of these implements such as the grinding mills and treadle operated pestle-and mortars can still be seen in use today in villages throughout China, unchanged for over two thousand years. Especially impressive are lead-glaze horses and multi-storied towers of monumental size. Much rarer are depictions of people, whether standing individually, or sitting down to a game of Liubo, or cutting up food in preparation for cooking.
In low-lying tombs subject to recurrent flooding, lead in the glaze dissolves, and deposits onto the surface of the vessel when the waters dry up. Repetition of this process over the millennia produces a hard, transparent integument possessed of an attractive, silvery iridescence, which is much sought after by collectors. In addition, deposition of minerals can lead to a yellowish encrustation which forms part of the patina. (Iridescence appears to be found only on green pieces.) Attempts to imitate iridescence on forgeries by subjecting the glaze to acid leads to a soft white layer which is easily scraped off, revealing dull denatured glaze beneath. Removal of natural iridescence by chemical means leaves a lustrous, undamaged glaze surface. Pieces from dry tombs can survive in mint condition.
Han lead-glaze wares provide an invaluable record of the everyday life of people from that era, and their beauty and variety render them eminently collectible.