Read

research

What do birch trees and the Bronze Age have in common – And what connects Babel and the Bible with Bitumen? Sometimes, tesa Analytics answers odd questions like these.

Text

Dr. Isabel Überhoff

At the cradle of science, said Albert Einstein, stands the mysterious. Exploring it is its motive, research is its tool. Thus, in addition to a large number of internal laboratory analysis jobs, tesa Analytics often also receives external inquiries from scientific institutes, for example from the area of antiquity research. In special cases, the lab jumps in with their experts and the latest equipment to reveal one or the other secret. For example, regarding the legendary Tower of Babel.

Bible? Babel? Bitumen!

The Bible literally makes history in two senses: On the one hand, as a Christian reference work; on the other hand, as a testimony of historical events. The erection of the Tower of Babel, which is described in the First Book of Moses, was an event that took place in real life: The remains of an impressive building were uncovered in today’s territory of Iraq in 1913. No laboratory in the world can prove whether the tower construction led to language confusion and divisiveness. However, we can research whether the building was constructed as described in the Old Testament (see info box) with bitumen (‘earth resin’) as a building material.

It is truly remarkable that more than 2,500 years ago, inorganic admixtures were apparently deliberately added to the bitumen, which certainly increased the adhesive strength on stone.

Dr. Christian Brinkmann, Head of the tesa Analytics Laboratory

The tiny rock sample from the Münster Bible Museum comes from the German archaeologist Dr. Robert Kaldewey, who discovered the remains of the tower in 1913.

A fragment of one of the ancient Babylonian bricks from the fund of the Bible Museum in Münster was to provide information about traces of a black substance attached to it. High-tech methods – such as infrared spectroscopy, micro-tomography and scanning electron microscopy – were used before Dr. Christian Brinkmann, Head of the tesa Analytics Laboratory, was able to confirm that the biblical building instructions did make sense: The bricks of the mighty tower have been unequivocally bonded with natural bitumen.

Where does bitumen come from?

Bitumen or ‘mineral pitch’ forms in long geological periods due to the evaporation of the lower-boiling parts of crude oil and is therefore also called ‘natural asphalt’. When heated up, bitumen becomes kneadable, then viscous, and finally thin at temperatures around 150 degrees. After cooling, it returns to its original semi-solid state. It was produced already in ancient times and because of its sealing and malleable properties it was used for various handicraft purposes.

Building instructions from the Bible

During excavations, the remains of several towers were found, which had been erected during the rule of King Nebuchadnezzar II (6th Century BC). One of them was particularly impressive with a floor area of more than 8,000 square meters and a height of probably 75 to 90 meters. For the construction, people used “brick as stone and earth resin as mortar” (Genesis 11.3). However, bitumen also plays a decisive role in other, at least equally significant, biblical passages. It is said, for example, that Moses’ mother abandoned her son – who later received the Ten Commandments – as an infant in a cane basket, which she had glued “with earth resin and pitch” (Exodus 2.3), on the banks of the river Nile, where he was then found and adopted by a pharaoh’s daughter. It’s hard to imagine what would have happened to Moses if bitumen hadn’t waterproofed the basket. Speaking of which: According to the Bible, Noah’s Ark was also sealed with mineral pitch by its builder (Genesis 6.14). In the Middle East, it was known as an integral part of shipbuilding 12,000 years ago.

An all-purpose glue: birch pitch

However, discoveries without any reference to the Bible also find their way to tesa. A Stone Age dagger from the local archeology department of the Lower Saxony region Schaumburger Landschaft has currently been brought to the laboratory. The approximately 4,000-year-old object is waiting to be examined. “In special cases – and if our capacities allow it –, we are happy to respond to such inquiries,” says Laboratory Manager Dr. Christian Brinkmann. 

Rather profane than sacred: The finder had discovered the sharp-edged flint stone in the clayey soil while working on the foundations of his home. The grip shell is missing. Was it once fastened with raffia or leather straps? Or did the historic all-purpose birch pitch adhesive hold the blade and handle together? To answer these questions, you need state-of-the-art equipment and high-tech analytics.  Brinkmann’s team has therefore examined the accidental archaeological find with instruments that allow chemical analyses at a magnification of up to 500,000 times.

The 11-cm long antique dagger is currently being examined at tesa.

An ancient witness made of stone

The recordings show that residues of an organic substance adhere to the stone. Its structure strongly suggests that it was once viscous – it could well be birch pitch. “Only once we’ve analyzed it in more detail and compared our results with another birch pitch sample will we finally know more about it,” explains Dr. Christian Brinkmann. One thing is certain: Once all analyses are completed, the dagger will be returned to the finder, who wants to make it available to the local museum.

Dr. Christian Brinkmann, head of the tesa analytics laboratory, evaluating the results of the scanning electron microscope.

What is birch pitch?

The brew obtained from birch bark is the first glue that humans have ever home-made and used. The history of bonding dates back approx. 200,000 years and thus to the Paleolithic Age. The whitish bark of the birch tree contains Betulin, which can be extracted as an adhesive by heating it to 340 to 400 degrees. It is not clear how exactly the Stone Age people did that: Maybe by rolling up the bark tightly and then covering it with ash in an earth trough and carbonizing it? At least that’s what science assumes today. Archaeological finds show that birch pitch was the glue of choice for tens of thousands of years. It was found during excavations at many camps and settlement sites in the Middle and New Stone Ages. Even in the Middle Ages, it was used for shanking, patching, or sealing. On various occasions, remains of birch pitch with tooth prints have been found. One might wonder then if the blackish mass was mankind’s first chewing gum! Since Betulin has anti-inflammatory properties, it could certainly have been useful for oral hygiene.