History, Politics And Current Affairs

Old finds with new revelations: Viking buildings had glass windows

Previously, it was believed that glass panes first came to Denmark in the Middle Ages. But a new research article from the National Museum has disproved that.


Glasruder came to Denmark much earlier than the researchers were aware of. Illustration of a piece of glass from Tissø: CS Andersen, Moesgaard Museum/T. Sweetie. 3D graphics of hall at Tissø: Arkikon / National Museum (Photo: © undefined)

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Frederik Brund Flintegaard
TODAY AT 15:58
The notion that the Vikings gathered and drank mead in very dark halls and temples in the Viking Age should perhaps be revised.
New research from the National Museum shows that Danish Vikings had glass panes in their buildings that lit up the rooms.
Mads Dengsø Jessen, who is a senior researcher at the National Museum and one of the authors behind the new research article, says that the research has revealed new information about the Danish arrival of the glass panes.
- Previously, it was believed that glass panes first came to Denmark in the Middle Ages, when churches and castles were built in that period.
- But analyzes of the fragments of glass that we have found have shown that they originate from the Viking Age several hundred years earlier, he says.

Mads Dengsø Jessen, senior researcher at the National Museum and one of the authors behind the research article, with a piece of glass from the Viking Age. Photo: John Fhær Engedal Nissen, National Museum.
Old finds – new revelations

The glass fragments have been found in connection with excavations of, among other things, Viking Age noblemen's farms over the past 25 years.
The excavations have taken place in Sweden and Germany but also in Denmark - including at Tissø in West Zealand.
The National Museum has therefore known about the glass fragments for many years, but it is only recently that they have been analysed.
The Vikings used the glass panes to create a special incidence of light inside
MADS DENGSØ JESSEN, SENIOR RESEARCHER AT THE NATIONAL MUSEUM
The analyzes threw up some interesting conclusions, says Mads Dengsø Jessen.
- We knew that the pieces of glass, which are usually dated to the Middle Ages, were found in locations that were not in use at all during that period. And that surprised us, he says.
This prompted Mads Dengsø Jessen and the rest of the research group, which consists of conservator and glass historian Torben Sode and head of research Bernard Gratuze from the University of Orleans in France, to investigate the glass fragments more closely.
- The glasses have a kind of chemical fingerprint, and with the help of a laser beam you can decode where and when the glasses were produced, he says.
The analysis revealed that the fragments were from the Viking Age, which according to the National Museum stretched from the year 800 to 1050, and probably produced in present-day Germany or France.
The function of the windows

The glass fragments found from the historical excavations are no larger than a fingernail, but they have previously formed larger panes of glass.
However, the panes were not transparent as we know them today.


Here are a number of examples of the fragments of glass that have been found in connection with the excavations. Photo: The National Museum
Mads Dengsø Jessen explains that many panes were matted mosaics in various green and brownish colours. In other words, you couldn't see directly through them.
We have a picture of the Vikings as some who went out to rob themselves of what they needed. I can't imagine what happened to the glass panes
MADS DENGSØ JESSEN, SENIOR RESEARCHER AT THE NATIONAL MUSEUM
But that wasn't the function of the glass panes in the Middle Ages either, he explains.
- The Vikings used the glass panes to create a special light inside. It could help mark people's authority by letting the incident light shine on them.
- They also often let the light fall on important places in a room if you wanted to emphasize something, he says.
Can change viking views

The new research can change the view of the Danish Vikings in several ways, believes Mads Dengsø Jessen.
First of all, it can push the notion of the Vikings as primitive.
- We have a picture of the Vikings as some who went out to rob themselves of what they needed.
- I can't imagine that has happened to the glass panes. The craft is so specialised, that they must have brought in craftsmen from the south of Denmark to install the windows. Or they may have learnt the technique themselves in the late part of the Viking Age, he says.
Mads Dengsø Jessen sees the way of glass panes to Denmark as an example of peaceful trade relations between the countries in the Viking Age, which was otherwise 'a relatively violent period in history'.
The research results also say something about the Vikings' connections to the rest of Europe, explains Mads Dengsø Jessen.
- This peaceful trading relationship shows that Danish Vikings were more closely connected with the rest of the European continent than we thought, he says.
The results of the new research have been published in the scientific journal Danish Journal of Archaeology.

jemhouston wrote: ↑Fri Oct 06, 2023 8:44 pm Glass making isn't simple. It would be interesting to find out how they got the idea.

LIGHTNING GLASS! (FULGURITE) HOW IT’S FORMED AND WHERE TO FIND IT
by DON GERIG
January 20, 2022, 9:18 pm
Have you ever heard of lightning glass? You may have heard it called by another name, fulgurite. This beautiful material is one that has a mystifying background to how it’s created and the differences between the types of fulgurites.

You might be surprised to know that there are many regions in the United States where lightning glass is located. There also are some incredibly interesting facts that scientists have learned about this material due to intense study of them as well as some mentions in pop culture.

What exactly is lightning glass?
what is fulgurite lightning glass
credit: Wikipedia

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Lightning glass typically occurs when lightning strikes a sandy beach. Though there are other causes that lead to the creation of this rock, this article will focus on this main one. Also known as fulgurites, this rare natural glass is made up of minerals that are rich in silica, such as the materials that come from soil, rocks, and sand.

The lightning bolt will go through the sand and then melt the silica within it into a liquid form. It cools and hardens fast, then leaves a thin glassy tube behind. The outside typically is rough and the inside is smooth.

When you find lightning rock underground, it can be shaped like tree roots and trace the zigzag path of the lighting bolt that led to its creation. They can be extremely delicate and have walls that are no thicker than 1 to 2 millimeters. Large fulgurites sometimes are taken from the ground in several pieces, then they are glued together so that they’re in the original shape.

Fulgurites in the United States
fulgurite located in Oregon
credit: Wikipedia


Now that you know what fulgurites are, you may be wondering where exactly to find these beautiful glassy treasures. Sand and rock lightning glass are generally found in environments that are dry with higher quartzite content in the sand or rocks.

Deserts, beaches, and high mountain areas are places to look for lightning glass. Wherever lightning strikes the ground, there is potential to form fulgurites, but, certain areas with the right minerals present in the rocks and dirt may be more conducive to making these formations.

Looking for lighting glass is challenging because of its rare, sometimes delicate physical nature. But, don’t give up! When you find lightning glass, it can be very exciting!

Searching for Sand Fulgurites
lightning glass fulgurite
Sand fulgurites tend to be rough with some partially melted sand in them. Deeper sand may produce longer tubes of fulgurite up to 30 inches. These tubes of glass that form in the beach sand during a lightning strike are challenging to find.

Lets face it, fulgurites are rare. If you are hunting for them, be prepared to commit some time to the endeavor. If you are looking for sand fulgurites, focus on beaches nearly anywhere from New England to Florida on the eastern coastline of the US.

Florida in the Tampa Bay area receives some of the highest lighting activity in the US. This presents opportunities for finding lightning glass with more frequency than other places. Several people have had success finding sand fulgurites in the Florida pan handle.

Deserts of the Southwestern US have ideal conditions for lightning glass to form. Searching desert areas in Utah, Nevada, and New Mexico with dry sand that is free of silt or clay can be good places to start.



Extra care should be taken when excavating sand fulgurites. These tubes of lightning glass are very delicate and can break easily. Being aware of this will help you preserve a more complete sample of lightning glass if you come across it at a beach or desert.

You should know how much of an anomaly lightning glass is and that you might not be able to dig one up with ease. On the other hand, there is a chance that you’ll come across this glass above ground since it withstands erosion.

Fulgurites in the Mountains?
Mountain peaks are places that naturally receive heavy lightning activity. This makes them ideal for rock and mineral hunters to look for rock fulgurites.

Mountain tops that have higher quartzite content may be more likely to have fulgurites, but they can be found in places with different mineral compositions. So strap on your hiking boots, rock fulgurites are more likely to be found at the top of mountains, not the base!

If you are looking for rock fulgurites, mountain peaks that get frequent lightning are good places to start. You may come across a vein of lightning glass in areas that once had a lot of lightning activity. Since mountain tops are higher up, lighting strikes can be intense, making fulgurites possibly more common in these areas.

Searching mountain peaks within the Cascade Range may offer up some rare lightning glass finds. Other high peaks in the Rocky Mountains and the Wasatch Range are possible areas to look for rock fulgurites.

where to find lightning glass
Facts About Lightning Glass
Here are some fun and intriguing things you likely didn’t know about fulgurite.

“Fulgurite” is a word that comes from the Latin root word “fulgur”, which means lightning. This refers to the process which makes this type of rock.
Other terms that are used interchangeably for lightning glass in certain areas are lightning rock and lightning stone.
Once lightning strikes the earth, it creates a heat that is five times hotter than the temperature at the surface of the sun. This allows for the minerals to change form.
The heat is able to fuse the clay and silica sand that’s at the site in order to make fulgurites.
Fulgurites are considered to be among the more rare occurring rocks. Remember, high heat and pressure is required to form them (making them metamorphic rock) and they’re made up of preexisting rocks. The sand or other material must hit more than 1400 degrees Celsius in order for this to work.
Lightning glass consists of glassy, hollow tubes that are classified as a type within the mineraloid lechatelierite. This means that they don’t have a crystal structure.
Lightning rock is not only made from the lightning that occurs during thunderstorms. It’s also created after meteor strikes and atomic blasts. Another way in which fulgurite forms is when human-made high voltage devices fall to the ground.
A fulgurite can get up to several centimeters in diameter. They are usually less than 10 feet long, though some of these magnificent cylindrical tube rocks can get up to 66 feet long!
The 2002 movie starring Reese Witherspoon, Sweet Home Alabama, featured an iconic scene in which two main characters find lightning glass on the beach. The explanation given by one of them is actually quite accurate, which you don’t often find in movies when it comes to scientific phenomena.
You might encounter irregular structures that occur due to the fact that the tubes collapse before they can fully form the glass. This may be disappointing if you find this instead, but it truly is just as cool when you see this!
Fulgurites that are made from rock typically are low in silica and are a variety of different colors depending on the rock’s composition. They are thin, glassy crusts that are on top of rock.

jemhouston wrote: ↑Fri Oct 06, 2023 8:44 pm Glass making isn't simple. It would be interesting to find out how they got the idea.