Medieval Bridges preserved with Sugar

Medieval bridge timbers found in Leicestershire are being preserved, thanks to sugar.

British Sugar has supplied more than 40 tonnes of liquid sugar to Leicestershire County Council, free of charge, to preserve an 11th century bridge discovered in Hemington.
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Once restoration is complete, the timbers – part of the largest medieval wooden structure in the region, after Lincoln Cathedral’s roof – could be put on display.
Timbers from three medieval bridges were found in Hemington Quarry in 1993 by a retired local GP, the late Chris Salisbury.

The County Council funded the University of Leicester Archaeological Services team to study and excavate the site. Sections of the 11th century bridge were so large that they had to be lifted by eight people.
Since the wet timbers were removed from the site, a painstaking conservation process has been taking place at Snibston Discovery Park, which involves immersing them in tanks of liquid sugar. The sugar crystals gradually replace the water and prevent the wood from warping.

Dr Julian Cooper, head of food science at British Sugar, said: “This project has been a source of genuine pride for British Sugar. Our long association with the River Trent at Newark made it a privilege to be involved in the restoration of the Hemington Bridge, which once spanned the same river. 

"Now we have reached the final stages of this 15 year conservation process, we congratulate the determination of those involved in safeguarding the bridge for generations to come.”

The bridge sections are thought to have been part of The King's Highway, a major national route linking London and the South with Derby and the North. They have gone on show at local science hub the Snibston Discovery Museum, where they had been kept in drying chambers for three years in the final part of the project.

"The carpentry and architecture of the 11th century bridge represents a crucial moment in British building history,” said Site Director Susan Ripper. “It combines the earth-based building technology of Anglo-Saxon England with the timber-frame technology which became commonplace a century later."

Results of an investigation into the bridges' structure and historical context have been revealed in an accompanying book launched alongside the display.

"The timbers are a rare testament to the engineering skills of the early Medieval period and illustrate the importance of the road networks to the economy of the time," said the University's Lynden Cooper. "They also provide unique evidence of Saxo-Norman woodworking methods."

Ernie White, Cabinet member for Community Services, said, “It’s amazing to think that timbers from a Norman bridge are being preserved with sugar - and that they could eventually be displayed to the public. I’d like to thank British Sugar for their generosity in supporting this project and for helping to ensure that future generations will be able to learn more about this fascinating find.”

Eggs not used to build medieval bridge in Prague, researchers find

No eggs were used during the construction of the 14th century Charles Bridge, the oldest stone bridge in Prague, researchers from Prague's Institute of Chemical Technology (VSCHT) have confirmed, its spokeswoman Ivana Pickova said yesterday.

The research team thereby refuted its previous research that, on the contrary, proved the presence of proteins from egg whites in the bridge.

"No eggs were used in the mortar for Charles Bridge," Pickova said.

However, scientists from the VSCHT, claimed in the autumn 2008 that they had succeeded in scientifically confirming the legend saying the medieval masons added eggs to the mortar during the bridge's construction.

Other scientists opposed this idea last year. Richard Prikryl, from Charles University's Faculty of Natural Sciences, said last May that experts had analysed the mortar from Charles Bridge by infrared spectroscopy that had not proved any traces of organic additives.

They were not added to the mortar for technological reasons, Prikryl stressed then.

Biochemist Stepanka Kuckova, from the VSCHT, who participated in the original research, challenged Prikryl's method as not sufficiently precise.

The scientists also reiterated that the masons of Charles Bridge had used "Roman mortar." It abounds in the qualities of modern construction materials, that are used for building bridges currently, in terms of strength, hardness and resistance to water.

The research team has also found out that the original inner structure of Charles Bridge is in a very good shape in spite of being 650 years old, Prikryl said.

A thorough reconstruction of the Charles Gothic bridge decorated with some 30 statues of saints mainly in Baroque style, is underway. It was launched in August, 2007.

Some experts, including the Culture Ministry's inspection, have criticised the repair works as unprofessional harming the unique sight. Heritage protectors and the City Hall that are responsible for the repairs have dismissed the criticism.

Luckily, one of the major tourist attractions in the Czech capital has never been completely closed during the reconstruction.

New Insights into the Medieval Construction of Charles Bridge in Prague

Builders of Prague's Gothic Charles Bridge used modern methods
12 May 2009
CTK (Ceska Tiskova Kancelar)

The builders of the 14th century Charles Bridge in Prague used modern methods that are only ascribed to their present-day colleagues, Richard Prykril, from the Natural Sciences Faculty of Charles University, said in a lecture today.

He said this is proved by the research into the bridge in which he has participated since 2002. The construction of the bridge was ordered by King of Bohemia and Roman Emperor Charles IV (1316-78). The foundation stone was laid on July 9, 1357.

The reconstruction of the Gothic bridge decorated with some 30 statues of saints mainly in Baroque style, one of the major landmarks of the capital, was launched last August and it is to be completed in mid-2010.

Prikryl said medieval builders used to add additional agents to the mortar of the masonry that fills the bridge's interior by which they improved its quality.

Similar procedures were used by ancient Rome builders but scientists have believed to date that these technological skills disappeared with the fall of the Roman Empire.

"We maintain that there is no 1000-year-long gap in knowledge, but that it was a very carefully guarded know-how of construction works," Prikryl said, pointing to the Charles Bridge masonry.

He said scientists were surprised by the quality of the masonry. "They created a masonry whose properties are similar to modern construction materials which we describe as light construction concretes," Prikryl told CTK.

Such material is light, but at the same time firm. Prikryl said one cubic metre of Charles Bridge masonry weighs only about 1850 kilograms, but it lends great stability to the bridge.