Glass windows could be found in Viking-Age Denmark and Sweden, study finds

New research has revealed that the Vikings had windows with glass panes as early as the 9th century. While glazed windows are associated with medieval churches and castles, we have plenty of examples from Viking-age Denmark and Sweden.

A research team led by a conservation expert from the National Museum of Denmark makes the claim in an article just published in the Danish Journal of Archaeology. They did so by re-examining over 61 glass fragments found from six Viking-age sites.


“Several fragments of glass windows found on important Viking Age sites in South Scandinavia, made us wonder if it was just a mere coincidence that they were there,” says Torben Sode, the study’s lead author who first noticed the special find material. “And it wasn’t, they can be dated to the Vikings Age and most likely must have been in use in that time-period as well.”

Window Glass found in Haithabu in Germany. Image courtesy the National Museum of Denmark

What makes the discovery so startling is the fact that glass windowpanes were not prevalent in Denmark until several centuries later when medieval churches and castles were constructed. Once again, this new knowledge spotlights the fact that the Vikings were far more advanced than they are often depicted.


“This is yet another shift away from the image of unsophisticated barbaric Vikings swinging their swords around,” adds National Museum’s senior researcher Mads Dengsø Jessen. “In fact, we are talking about a cultivated Viking elite with royal power that equalled that, for example, of Charlemagne, king of the Franks. This is something that is often omitted in the simplistic Hollywood portraits of Vikings,”

Viking Age glass

The research is based on analyses of fragments of glass panes, which were found over the past 25 years in six different excavations – five in southern Scandinavia and one in Hedeby in northern Germany – of the farms of Viking noblemen, pre-Christian temples and early urban environments.

We have known about the glass for many years, but no one analyzed it until now. This is because we only associated early window glass with the Middle Ages, therefore assuming that the glass could not originate from the Viking Age, but must have been the result of ‘pollution’ from later periods.

Window Glass fragments found at Viking sites. Image courtesy the National Museum of Denmark

Now, however, chemical isotope analyses of the glass panes show that the glass was made of soda glass, a practice from Egypt and the Near East, or potash glass that was made in Germany, and can be dated to between the years 800 and 1150.


Pillaged or purchased?

Nothing indicates that the Vikings could produce glass for windows, but there is no doubt that they were familiar with the material from Europe, where glazed windows had long been a feature of churches and imperial halls: for example in Anglo-Saxon and Carolingian culture, where we have discovered exactly the same type of glass that has now been found from the Viking Age in southern Scandinavia.

This is hardly a coincidence, since the Vikings looked south for inspiration. Mads Dengsø Jessen explains:

We know that well-known Vikings, such as Harald Klak, visited the south, where the Vikings had a political network and close trade links. So, 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.


There is also a suspicion that the Vikings may have expropriated the window glass from monasteries and churches during raids. However, according to the researchers, this is less likely, given that the glass was found at several different Viking sites, while the chemical signature proves that the glass panes originate from different parts of Europe and the Near East. In other words, it is most likely that the Vikings acquired it through trade.

Map over Vikinge sites where Window Glass fragments have been found. Image courtesy the National Museum of Denmark

Glass windows in the halls of Viking noblemen

When it comes to the Vikings, glass windows were reserved for the upper echelons of society and for religious use, as was the case in the rest of Europe. Therefore, according to Mads Dengsø Jessen, there may have been glass windows in the iconic hall buildings of the Vikings.

They were not the large, transparent windows we have today, but probably smaller windows, possibly composed of flat pane glass in different shades of green and brown. As Mads Dengsø Jessen points out, the idea was not to be able to look out, but to create a colourful inflow of light into the building. It leads the researchers to ask whether or not some of this glass would have been used in pre-Christian religious sites. They write:

The glass in the church windows was perceived as a special, magical material, which could let in the sunlight and illuminate the room, whilst also keeping the cold, wind, and rain out, whereas windows in aulas would underline the well-connected and exclusive character of the royalty residing there. This suggests that there possibly were one or more small windows with glass panes in the pagan cult buildings, like in the stave churches and the early stone churches in Jutland, just as the hall-buildings would be illuminated through glassed windows as were the aulas of the continental palaces.


The article, “Viking Age WindowsA reassessment of windowpane fragments based on chemical analysis (LA-ICP-MS) and their find contexts,” by Torben Sode1, Bernard Gratuze and Mads Dengsø Jessen, appears in the Danish Journal of Archaeology. Click here to read it.

Top Image: A piece of Window Glass fragment from the Viking Age. Photo: John Fhær Engedal Nissen, the National Museum of Denmark.