AN EIGHTH CENTURY TREATISE ON GLASS

Kitab al-Durra al-Maknuna (The Book of the Hidden Pearl)

of Jabir ibn Hayyan (c. 721–c. 815)

ON COLOURED GLASS, ON LUSTRE GLASS, ON GEMSTONES AND PEARLS

Part Four

ASSESSMENT OF KITAB AL-DURRA AL-MAKNUNA

Islamic Glass Industry at the Time of Jabir

When Jabir was writing his treatise on coloured glass in the eighth century, there were in Iraq, Syria, Egypt and Iran thriving glass industries. Glass originated in this area since ancient times but it flourished and great innovations were introduced during Jabir’s time and in later centuries.

Our knowledge about Islamic glass is based partially on Arabic literature; but we are indebted to the archaeological excavations that were undertaken at several sites like al-Raqqa, Basra, Samarra, Fustat, Nisapur, Palestine, at several other locations in the Near East, in Europe and in the Far East [1]. Furthermore, world museums hold great treasures of Islamic glass and they contributed considerably to our knowledge through the special exhibits that are organised from time to time and the published catalogues that include valuable studies by glass specialists.[2]

We shall not discuss here the production of ordinary or un-coloured glass and shall limit ourselves to the production of coloured and lustre painted glass that are the main themes in Kitab al-durra. But we may mention in passing that at the time of Jabir and later, clear glass of great purity was produced according to al-Biruni,[3] who always quotes Arab poets in illustrating his statements.[4]

Coloured Glass

The first part of Kitab al-durra deals with the production of coloured glass that was known during the ancient civilizations of Babylonia and Egypt. The earliest recipes for coloured glass before Jabir were given in the Assyrian Cuneiform Tablets from Nineveh from the Library of Assurbanipal (668-626 B.C.E.). These tablets were translated into English [5] and German.

Despite the difficulty in translating the texts of the tablets, it is evident that glass of various colours was produced and the recipes included metallic oxides among other ingredients.

The tradition of making coloured glass continued throughout the later centuries and there are naturally a few similarities between the recipes used. Jabir as an accomplished chemist gave mature and clear quantitative recipes, He had utilized the practical knowledge of his time but he could not obviously copy any recipes from the buried Assyrian cuneiform tablets that preceded him by about fourteen centuries.  He presented reliable recipes utilizing his own immense chemical knowledge while taking into consideration the technical skills of the glass-makers of his time.

The recipes in Kitab al-durra are unique in that they describe the production of high quality coloured glass which is cut into artificial gemstones. These stones are different from those which are obtained by the dying of pebbles, small rock crystal pieces or beads, which are described also in Kitab al-durra.

The only other written recipes that preceded Jabir, beside the Assyrian tablets, were those of the papyri of the fourth century C.E., but the papyri of both Leyden and Stockholm are devoid of any recipes for the production of coloured glass.[6]  No work in Western literature discusses the colouring of glass in a similar manner until the appearance of the book of Neri in 1662. [7]

Islamic Lustre Painted Glass

The Present Picture According to Present Scholarship

Lustre-painting, which is characteristic of Islamic glass and pottery, is a metallic sheen applied on the surfaces of glass or pottery objects. Its origin has been the subject of discussion amongst historians, the suggested centres being Iraq, Syria, Egypt or Iran. It may be difficult to arrive at a definite answer, but we know from existing findings that this technique was applied on glass by Egyptian and Syrian workers at about the same time in the 8th century C.E.[8] The earliest lustre painted glass cup from Fustat is dated 163/779 and the earliest one from Damascus is dated 170/786.[9] But these two dates are only suggestive. The technique must have been applied at earlier dates in the same century.

Chemical analyses of a group of luster-ware glass fragments in the Corning Museum of Glass confirmed that the stained surfaces contained silver and copper. [10] Brill, who conducted the tests, says: “We now believe, from our analyses, that the indispensable ingredi­ents for staining the glasses were a silver com­pound, a copper compound, a reducing agent, and a vehicle with a thickening agent.”

Brill further states that the paste is painted onto the surface of the object, which was then re-fired at a moderate temperature. During the re-firing, the silver migrates through the surface into the body of the glass. Upon becoming reduced chemically to minute colloidal particles of metallic silver, it imparts a permanent stain just beneath the surface. The color of the resulting stain depends primarily on the amount of silver pres­ent and the extent to which the chemical reduction had proceeded. It could range from a lemon yellow to strong amber. Evidently the presence of cop­per shifts the color further toward the amber shades.[11]

Silver staining appears in Western Europe on medieval stained-glass windows, more than five centuries after this technique was applied in Syria and Egypt. The earliest known example is in the Norman church of Le Mesnil Villeman (a village in the Manche, north of France) and is dated 1313, By the 1320s silver stain was widely used, and the technique has been continuously employed since then. It survives today in modern stained-glass windows and art glass, in which yellow stains are still based on colloidal silver, sometimes accompanied by copper.[12]

Jabir’s Recipes and the Results of Modern Analyses

The relationship between the chemist and the artisan in stained glass is explained by al-Biruni. After discussing the various colours which arise from metallic oxides, he says:” They have many methods and disclosures on the composition of basic glass and the quantities of the colouring materials; but none of these can be considered right except by observing the work of the distinguished artisans and by actually getting involved in the work and practicing it by doing experiments on the compositions. Glass, enamel and ceramics are close to each other and they have common techniques in pigments and in the methods of colouring.”[13]

Some modern scholars perceived that there should be a relationship between the methods of colouring and Arabic chemistry, and some had expressed an interest in knowing whether the chemistry of Jabir ibn Hayyan had any bearing on the development of lustre painting.[14] This interest arose from the fact that lustre-painting on glass first appeared at the same time when Jabir was active as a chemist when he wrote Kitab al-durra and many other works. Jabir was the chemist of the Caliph Harun al-Rashid who made al-Raqqa his second capital and during whose reign the glass industry was established in that city.

In one of his papers, Henderson suggested that Jabir ibn Hayyan must have exercised some influence on the constituents of glass in al-Raqqa in his capacity as the chemist of the Caliph while he was residing there.[15]

Alan Caiger-Smith wrote also a chapter on alchemy in its relationship to lustre-painting, drawing attention to the similarity in materials used by alchemists and lustre-makers.[16] The name of Jabir was of course mentioned.

The above results reported by Brill, correspond with the recipes of Jabir. In part two of this paper we found that the most important material in the recipes for painted lustre is burnt silver. It occurs in about 72 percent of the recipes, and copper with its various compounds is most prevalent and it occurs in most of the recipes also. This correspondence between the recipes of Jabir and modern analysis is so important that it merits a further elaboration.

Dyed Gemstones and Pearls

A part of Kitab al-durra is devoted to the dyeing of gemstones.  In addition to the recipes for dyeing, Jabir provides details of the dyeing technique and he describes the ovens that are used for this purpose.

Dyeing of gemstones occurs in the Stockholm Papyrus. And although there are numerous recipes, yet the technique of dyeing is not mentioned, and the ovens employed are not described.

The treatise discusses also the whitening of pearls and the making of artificial ones. For thousands of years seawater pearls were retrieved by divers working in the Persian Gulf. Al-Biruni in Kitab al-Jamahir discusses pearls in great detail. He describes also the whitening of pearls. He quite often quotes al-Kindi and Nasr  who wrote important treatises on pearls and gemstones, that are now lost,

In the region of pearl production around the Persian Gulf there are local traditions about the whitening of discoloured pearls. Al-Jahiz (c. 781 – 868) speaks about these traditions among the people of Bahrain. [17] The information cited by him is mentioned also by al-Biruni who attributes it to Nasr.

The cleaning of discoloured pearls was an ancient art, and we find some recipes in the Stockholm Papyrus. They are of similar nature as those of Jabir but without exact correspondence. It is unlikely that Jabir was aware of the contents of the Stockholm Papyrus which was found buried inside a tomb in Upper Egypt. Neither also al-Kindi, Nasr, al-Jahiz or al-Biruni and other Arabic authors  were aware of them. Some of the recipes like that of placing the discoloured pearl inside a dough and feeding it to a chicken were prevalent recipes circulating in the area since ancient times, and some of them were of a chemical nature that were formulated and written by the chemists themselves.

The same information applies to the manufacture of artificial pearls. Both the Stockholm papyri and Kitab al-durra contain few recipes on artificial pearls without a textual correspondence between them.

Epilogue

It seems that Kitab al-durra al-maknuna of Jabir ibn Hayyan is the only treatise of its kind that deals with lustre-painted glass. The known Latin books of recipes do not discuss lustre painting of glassware or of pottery. Such wares began to be produced in north Italy about 1300. And both copper and silver lustre techniques are said to be included in a fifteenth-century manuscript of recipes, now at Munich.[18]

Recent analysis of luster painting on glass and pottery had proved that the main ingredi­ents for staining were silver and copper. This analysis corresponds with the recipes of Jabir ibn Hayyan in Kitab al-durra al-maknuna.

The discovery of this book of practical chemical recipes of Jabir ibn Hayyan dissipates the wrong notion of some historians that he was only an alchemist whose writings were vague and unintelligible. It also refutes the prevailing assumption of some historians of science that the Latin books of technical recipes that appeared in the West before the twelfth century had no parallels in Arabic literature. In fact there is no parallel to Kitab al-durra in practical chemical recipes in Latin literature.