The Prague City Hall Clock, also known as the Apostle Clock or the Old Town Astronomical Clock, dates back to 1410 and is one of the most famous sights in the Czech capital. It doesn’t just show the time; it also displays astronomical conditions such as the position of the sun and the corresponding sign of the zodiac, the phases of the moon and twilight, and the Tropic of Cancer and Capricorn. To ensure that the time is always correct for onlookers, BECHEM looks after the different components of the clock’s mechanism, making sure that they run smoothly.

*Albert Einstein (1879–1955), Physicist and the world’s most famous scientist of modern times, University professor of theoretical physics at the German University in Prague (1911–1912).

What is time? Time is a fundamental physical quantity in our world. It runs inexorably in one direction. Time describes a sequence of events and thus the progression of the present from the past into the future. We divide them into units and measure them – seconds, minutes, hours. For centuries, we have been measuring time through clockwork mechanisms.

In the Middle Ages, clocks were used mainly for religious purposes. Various bells of the church and city towers were used to announce, for example, the prayer times of the monasteries, the opening times of city gates or the court and market times from the towers. The astronomical clock in Prague is considered to be one of the most famous symbols of that time, because it demonstrates the very complex connection between the developing machinery industry and mathematical, astronomical, astrological and philosophical knowledge. It is a masterpiece of Gothic science and technology and a valuable cultural monument located on the southern wall of the City Hall in Prague’s (Czech Republic) old town and admired by millions of people from all over the world every year.

The Bohemian clockmaker and mechanic Nikolaus von Kaaden built the mechanical clockwork with an astronomical dial in 1410, according to the plans of astronomer Johannes Schindel. The calendar below the dial followed in around 1490 as part of the second construction phase. It was not until the 17th century that the figures were placed to the left and right of the dials. Over the course of six centuries, the clock stopped many times and was repaired several times. In 1760, for example, the clock was in very poor condition, but could not be repaired properly. In the 19th century, the figures of the twelve apostles were placed in the two windows above the dial, appearing every hour on the hour from 9 a.m. to 10 p.m. It was not until 1866 that the clock was reconstructed and restored. During the Prague Uprising in the last three days of the Second World War in 1945, the clock was badly damaged by direct shots and fire.

The Prague Town Hall Clock is a typical example of clock displays in the Middle Ages: on top, the dial containing time and astronomical displays; underneath, the calendar. The figures are to the sides. The apostle procession was installed later in the two small windows above the dials.

The Prague City Hall Clock was thoroughly restored in 2018 to commemorate the 100th anniversary of the founding of the Czechoslovak Republic. The focus of the restoration was on repainting, restoring wooden sections and applying long-lasting lubricant to the moving parts. BECHEM’s sales partner in the Czech Republic, LUBRICANT in Starý Plzenec, was contracted to find a suitable lubricant. “We were fascinated by the many individual parts of this 600-year-old clock when we saw it in the workshop. As many 15th century components as possible were to be used. We discovered that the bearings had been replaced in the 19th century and wooden parts had suffered fire damage at the end of the Second World War. However, many original gears still exist. The surviving documents show that the blacksmiths made the gears by hand. And although every tooth is unique and therefore different, the clock has remained accurate for more than six centuries. Several blacksmiths made the columns that support the mechanism. Their signatures are still legible on the columns today,” Jiri Valdauf, responsible for technical support at LUBRICANT, enthuses about the unusual project.

“Anyone who keeps the ability
to see beauty will never
grow old.”

Franz Kafka (1883–1924),
German-language novelist, born in Prague

“Clocks are usually lubricated with low-viscosity mineral oil to reduce the friction coefficient. But the Prague City Hall clock works differently. Here, high-viscosity oil with high  adhesive strength and good low-temperature properties must be used to ensure reliable lubrication, while protecting the surface from dust. The operator prefers a lubricating oil because it is easier to apply oil to the areas that need lubrication. Further requirements included extended oil change intervals, excellent wear protection and very high aging resistance. The high-performance gear oil Berusynth GP 460 based on polyalphaolefin is the right choice for these conditions and meets all the requirements. This means that the Prague City Hall Clock works reliably and perfectly without relubrication, even in hot summers and frosty winters,” says Jiri Valdauf, explaining the choice of lubricant.

As a result of this significant reference, LUBRICANT, in cooperation with the clock maintenance specialist L. Hainz of Prague, was entrusted with the lubrication maintenance of all tower clocks in the Czech Republic.