In most regions in the Middle Ages, lead glass was used to produce small objects, ornaments and glazes; in some cultural circles it was also used to make vessels. In the early Middle Ages, it was mainly a mixture of silica and lead oxide. Later, the amount of lead oxide used for its production decreased.

The oldest beads made of lead glass come from Egypt, from the 18th dynasty (1450-1425 BCE). The first recipes for glass containing lead date back to the 7th century BCE, when they appeared in Mesopotamian texts.

In Europe, the recipe for producing lead glass was widespread from the 10th to the 14th century CE. It reached the Old Continent from Southeast Asia, most likely via the Silk Road. Glass based on this recipe was produced in the Iberian Peninsula, in the territories of present-day Germany, in Poland, and probably in Russia and the Caucasus.

'Due to the great popularity of lead glass in Central and Eastern Europe, this region is seen as key for its spreading. The period of the greatest popularity of this type of glass in these areas was the 12th century', says Aleksandra Pankiewicz, PhD, from the University of Wrocław.

'It has long been suggested that medieval lead glass ornaments found in Poland are of local origin. This is evidenced by both the large number of similar types of jewellery and the existence of a rich raw material base in the Olkusz area, which is conducive to the production of this type of products, but until now there has been no evidence for this', adds Ewelina Miśta-Jakubowska, PhD, from the Jagiellonian University and the National Centre for Nuclear Research.

There are lead deposits on the border of Małopolska and Silesia, exploited at least since the Iron Age, which was also recently proven by a research team led by Ewelina Miśta-Jakubowska. Research shows that these deposits were used as early as the 6th century BCE, and their exploitation peaked from the 11th century.

Researchers from the University of Wrocław, the Jagiellonian University, the National Centre for Nuclear Research, the University of Warsaw, the Jan Długosz University in Częstochowa and the Institute of Archaeology and Ethnology of the Polish Academy of Sciences, in collaboration with Juniata College in the USA, conducted analyses of lead isotope ratios in glass jewellery discovered in a stronghold in Wrocław and in a cemetery in Sypniewo (Masovian Voivodeship).

They published their results in the prestigious "Journal of Archaeological Science".

Several glass ornaments (rings and beads) from the stronghold in Wrocław, dated to the mid-11th - mid-12th century, were selected for analysis.

The findings from Sypniewo come from the grave of a young woman, dated to the 12th - early 13th century. The deceased was buried with numerous ornaments, of which five glass beads were selected for analysis.

'The artefacts found in Wrocław and Sypniewo confirm that lead glass jewellery was mass-produced in Poland, and the raw material came from Polish deposits on the border of Silesia and Małopolska. At the same time, no clear evidence of glass being melted from raw ingredients has been found. All studies indicate that jewellery makers used semi-finished products in the form of glass rods or discs, which could have been brought from elsewhere', describes Sylwia Siemianowska, PhD, from the Institute of Archaeology and Ethnology PAS.

Although there is ample evidence of the use of lead in Poland, especially near deposits in the Olkusz area, no workshops have been found so far in which glass was produced from raw material. Glass processing sites were found mainly in larger towns, often located far from the raw material sources (e.g. Wrocław - approx. 200 km from Olkusz, Sypniewo - 350 km).

'The places where the raw material for the production of lead glass was produced remain unknown. However, the results of the analysis of the lead isotope ratios indicate that the search for them should focus on the territory of Poland', the researchers emphasise.

Ewelina Krajczyńska-Wujec (PAP)

PAP - Science in Poland

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