LAZAWARD (LAJVARD ) AND ZAFFER
IN ISLAMIC AND WESTERN LUSTRE GLASS AND CERAMICS
Cobalt oxide was used for blue colour in lustre glass and ceramics during the early times of the Abbasid Caliphate and the later centuries. The Arabic word lazaward, Persian lajvard was used to denote this pigment. The word indicates also “lapis lazuli”, which is a stone with one of the longest traditions of being considered a gem. The ultramarine pigment from this rock, cannot be used for glaze because of its lower temperature resistance, therefore the word lazaward (Arabic) or lajvard (Persian) when used for lustre pigment must mean cobalt ore. 
There were mines for this ore on the south of Kashan in Persia,  and in Oman and Northern Hijaz . The ore was processed and sent to Basra and other ceramics and glass manufacturing centres in Iraq and other Islamic cities and was later exported to China and to Europe.
Towards the end of the nineteenth century it was still processed in the same traditional way south of Kashan. A. H. Schindler (the German-born British engineer who had spent nearly thirty years in Persia and was director of mines there), visited the mines in the village Kamsar, 19 miles to the south of Kashan, and he described the mining operation. The earthy cobalt contains about five per cent of metal. It is collected and washed with water, and the heavy sediment is made into cakes. The cakes, under the name of lajverd i Kashi, are exported.
The ore is reduced in the following way: ten parts by weight of the earth or ore (in cakes), five of potash, five of borax, are pounded together to a fine powder, and then made into a paste with concentrated grape juice (shireh), and formed into small balls or cakes. The balls are then put with pounded quartz into a sufar (earthen pot with wide opening) and exposed to heat in a furnace for sixteen hours. The metal gained in this way amounts to about one twentieth of the weight of the cobalt cakes employed.
To use the cobalt for colouring pottery it is ground into fine powder with an equal quantity of quartz.
Although cobalt blue was known in Islam for many centuries, it was not used in Italy until early in the fifteenth century. It was imported as the impure oxide, zaffre, from Syria through Venice and known as colore damaschino, (Damascus pigment). Since it was dutiable in many ports, there was considerable smuggling. 
In China, during the Yuan Dynasty (1271 to 1368), and the early period of Ming (1368 to 1644), the crude cobalt oxide was imported from the Kashan district of Persia and was known as Mohammedan blue (hui-hui ch'ing). 
Chemists and alchemists did not know the chemical composition of numerous materials before the age of modern chemistry. The word natrun, for example, was used to denote either potassium nitrate or sodium carbonate. The same applies to the word lazward or lajvard . It could mean either lapis lazuli or crude cobalt oxide. The common quality here is the blue colour only. In Western literature the word zaffer was used to denote this pigment. The etymology of the word indicates most probably an Arabic origin. This seems probable since this material was imported initially from Arabic lands.
The real composition of lazaward (lajvard ) or zaffer remained unknown until about 1735 when Georg Brandt of Sweden, who was studying the blue colour of glass, discovered that the colour was due to a new element, cobalt.
In Kitab al-durra al maknuna of Jabir ibn Hayyan which deals exclusively with the manufacture of coloured glass, production of lustre glass, and the manufacture of artificial gemstones and pearls, the word lazaward, indicating cobalt oxide pigment, occurred in more than twenty recipes, mostly for producing lustre glass. At the same period, during the Abbasid Caliphate, lustre glass was being manufactured in Basra and other Islamic cities.
Western literature of technical recipes dealing with paints and the staining of glass did not refer to cobalt blue until after the fifteenth century. This applies to the Compositiones Ad Tingenda Musiva, the Mappae Clavicula  and the Schedula diversarum artium of Theophilus.
The word zaffer was used extensively in Neri’s The Art of Glass in 1612. This is about eight centuries after Kitab al-durra al-maknuna of Jabir.
 Hess, Catherine. ‘ Brilliant Achievement: The Journey of Islamic Glass and Ceramics to Renaissance Italy’, in The Arts of Fire, ed. Catherine Hess, J. Paul Getty Museum, Los Angeles, 2004, pp. 1-33.
 Allan J.W. “Abu’l-Qasim’s Treatise on Ceramics”, Iran 11 (1973) pp.111-20
 Allan, op. cit.
 Allan, op. cit.
 Saliba, George, ‘The World of Islam and Renaissance Science and Technology’ , in The Arts of Fire, ed. Catherine Hess, J. Paul Getty Museum, Los Angeles, 2004, p. 57. Saliba is quoting from Pope, E. M. ‘Ceramics, Medieval’ in A History of Technology, ed. Charles Singer et al. Vol. 2, Oxford. 1954-58, pp. 284-310.
 Encyclopaedia Britannica, East Asian and Southeast Asian pottery > China > Ming dynasty (1368–1644)
 Webster's Dictionary (1913 Edition)
 A Dictionary of Scientists. Oxford University Press, 2003.
 Jabir ibn Hayyan, Kitab al-durra al-maknuna, B.N. MS Arabe 6915.
 Compositiones Ad Tingenda Musiva, edited and translated into German by Hjalmar Hedfords, Uppsala, 1932.
 Mappae Clavicula, A Little Key to the World of Medieval Techniques,
Translated and edited by Cyril Stanley Smith and John G. Hawthorne, transactions of the American Philosophical Society, Philadelphia, 1974.
 Schedula diversarum artium of Theophilus,
On divers arts : the treatise of Theophilus / translated from the medieval Latin with introd. and notes by John G. Hawthorne and Cyril Stanley Smith. Chicago]: University of Chicago Press, 1963.
 The Art of Glass, by Antonio Neri, translated with a commentary by Christopher Merrett. Edited by Michael Cable, The Society of Glass Technology, 2004.