A senior researcher at the National Museum of Denmark in Copenhagen has discovered that Vikings had windows with glass panes long before they were used in medieval churches and castles. 

Mads Dengsø Jessen has been collaborating with a team of experts, analyzing samples of glass fragments discovered at key Viking sites across southern Scandinavia. 

Working with conservator and glass specialist Torben Sode and research director Bernard Gratuze based at the University of Orléans in France, Jessen has published the results in the Danish Journal of Archaeology

As one of the earliest urban settlements in Denmark and northern Germany, Hedeby played a pivotal role in the trade routes of Viking and Slavic merchants. Photo: Frank Vincentz / Wikimedia Commons (CC BY-SA 3.0)

From Birka to Hedeby 

Their research is based on the analysis of 61 glass pane fragments found over the past 25 years in six different excavations. 

Five of these were located in southern Scandinavia, with sites including Birka in Sweden. Another was in Hedeby, situated in modern-day Schleswig, Germany.

These excavations spanned the farms of Viking noblemen, pre-Christian temples, and early urban settings.

The locations concerned are considered to have biographical depth, a term indicating that the sites would have been occupied and reoccupied over several centuries.

Groundbreaking findings suggest that glass window panes were not prevalent in Denmark until several centuries later when they were used in the construction of churches and castles. 

The new research highlights the fact that the Vikings were far more advanced than the bloodthirsty marauders they are often depicted to be. 

"This is yet another shift away from the image of unsophisticated barbaric Vikings swinging their swords around," said Mads Dengsø Jessen. 

"In fact, we are talking about a cultivated Viking elite with royal power that equaled that, for example, of Charlemagne, king of the Franks. This is something that is often omitted in the simplistic Hollywood portraits of Vikings." 

Originating from a Viking grave in Björkö, Sweden, the beaker is evidence of their appreciation for exclusive Frankish glass artifacts; pictured is a replica of the original piece. Photo: The Swedish History Museum, Stockholm (CC BY-SA 2.0)

Picking up the pieces 

While researchers and archaeologists have picked over these six sites for several years, no one has really thought to look more closely at the glass fragments. 

As window glass was so prevalent in medieval churches, it was simply assumed that the evidence found had mingled with that of the Viking Age and could not date back to before 1050. 

Chemical isotope analyses of the glass panes indicate they were made from Near Eastern soda glass or Northern European potash glass. 

This suggests they can be dated to well before the 12th century, predating the churches and castles of the Middle Ages. 

There's no current evidence suggesting Vikings produced their own glass for windows. However, they were evidently familiar with such materials from European locales, including the glazed windows in churches and imperial halls of Anglo-Saxon and Carolingian cultures. 

The glass from the Viking Age found in southern Scandinavia appears to be of this exact type. 

As Mads Dengsø Jessen points out, "We know that well-known Vikings, such as Harald Klak, visited the south, where the Vikings had a political network and close trade links."

"Of course, they were familiar with glass panes from the buildings of society's upper echelons there. It is thus also very likely that the Vikings also had glazed windows – a fact now confirmed by recent research." 

It's possible that during their raids, the Vikings might have taken the window glass from monasteries and churches.

However, the chemical signature of the glass from the six sites suggests it originated from various regions in Europe and the Near East. It's likely the owners obtained the glass via trade. 

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