For most tourists in Prague, visiting the Charles Bridge is pretty much at the top of the sightseeing list. The medieval stone bridge, completed in the 15th century, was a part of the royal route – the path Bohemian kings took to the Prague Castle for their coronations. It also served as a key trade route, and now, is perhaps the most international place in Prague. Alongside its immense historical and cultural significance for the Czech Republic and the Bohemian Kingdom, there is one myth around its construction that may warrant some head scratching.
A Bridge Made of Eggs?
It has been claimed that King Charles IV, the very man who ordered the construction of the bridge, called for raw eggs to be added to the bridge’s mortar. The idea was that this mortar would better hold the stones of the bridge together. I like to think about it like adding eggs to ground beef to help bind a burger. Since there were not enough eggs in Prague to carry out this construction task, Charles IV requested eggs from all over the Czech Republic. Unfortunately, in this request, there were a few misunderstandings. Some villages brought cheese, and those coming from the village of Velvary brought hard boiled eggs. Those from Velvary hard boiled their eggs in good faith: to ensure their safe transport to Prague. When they arrived in Prague, there were met with mockery and ridicule that still lingers today.
Unfortunately, while part of me hoped for there to be some truth in this tale, it is only a myth. , in an investigation carried out by researchers at Charles University’s Faculty of Science, they found that there were no traces of organic additives in the bridge’s mortar composition. Additionally, in investigating the structural composition of the materials used to build medieval bridges, like the Charles Bridge, it was found that the main binding product was comprised of various minerals, not eggs.
Egg-spiration for the Future?
Though a myth, this story still brings to light a new frontier in material production. In an age where building sustainably is a key demand, searching for sustainable building materials is the future of construction – specifically, concrete. Concrete is one of the , and, currently, its production has grave environmental consequences as it accounts for 8% of global CO2 (carbon dioxide) production. From using fossil fuels to fire raw materials such as limestone to mining for sand and gravel, industries and government leaders are finally scrutinizing the concrete industry for its negative environmental impacts.
In this push to make concrete more sustainably, researchers in Japan offer an interesting approach. An expert in the fields of recycling and concrete, Dr. Yuya Sakai at the University of Tokyo set out to see just how sustainable he could make concrete, going as far as to attempt making it out of . As it turns out, in the lab, it’s not not impossible. In his preliminary experiments, orange peels, coffee grounds, bananas, and Chinese cabbage were put to the test. For each waste product, Sakai and his team broke them down into small pieces and dried them out. Then, the researchers blended the dried food waste into a powder. They then mixed this powder with water and other binding agents before being hot pressed to turn the powder into a block. The beauty of this technology is that it both relies on materials that would otherwise be sent to the landfill, and it is biodegradable, meaning it can be returned to the Earth when it is no longer needed.
Of course, while this may seem like a dream come true – sometimes the lab is as far as these dreams can go. Unfortunately, this product’s ability to withstand the elements, as well as its structural integrity are yet to be determined for construction in the real world. However, there are other ways in which the concrete industry is . Whether it be through utilizing , in which the carbon emissions are turned into solid material, to using other locally sourced recycled material to that is incorporated in the concrete mixture, researchers and industry leaders have identified a number of pathways in which concrete can be produced more sustainably going forward.
To return to the Charles Bridge, perhaps myths don’t have to be permanent. Maybe there is a future in which organic materials are used as sustainable building blocks. For now, though, I’ll take my eggs over easy.
Eva Kellner is a recent graduate from the Faculty of Arts and Science, with a major in Environment. Her research interests include urban green spaces, urban agriculture, and outdoor community spaces - all as promoters of climate resilience among city-dwellers.
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