How are the ice layers created, and how does the rink's maintenance look like?

RTL Today has teamed up with PISA, the Luxembourgish science magazine, to reproduce their original videos in English for our site. Presenter Olivier Catani this week steps onto the massive concrete slab below the ice at the Kockelscheuer ice rink to see how it is cooled down and prepared for the season.

This video is part of the PISA series for RTL Today. Watch all English videos on RTL Play, or discover the wide range of subjects previously covered in Luxembourgish here (there are 13 seasons, mind you! We'll try and catch up...). Our previous episodes covered the history of the tramLuxembourg airport, explained how the coronavirus vaccine works, asked why traffic lights always seem to be red, investigated where our tap water comes from, looked at Luxembourg's railways since 1859, took a dive into the Moselle Valley and its underground Dolomite mines and more...

How the ice is formed

How can it be that there's solid ice at the Kockelscheuer ice rink in mid-August? Wouldn't it all just melt away? Here's how the site's cooling system works: A massive concrete slab is cooled down using a compression cooling system located below ground, explains Lex Fautsch, who is responsible for the rink's maintenance.

The system compresses a gas, which then expands, generating cold temperatures. This is then transferred to a glycol fluid, flowing through pipes to the concrete slab above. Once the concrete has cooled, ice masters then spray a small amount of water onto it, which freezes rather quickly. The ice masters have to work in pairs because the hose would be in the away otherwise. Several water layers are required to generate at least one centimetre of ice.

But why is the ice transparent, and not white? That's where chalk powder comes into play, sprayed over the concrete together with the water, creating a beautiful, white surface. But there's a problem with this technique: once the ice has melted, the team is left with powdered water. So a machine is put in place to try and scrape off the chalk at the end of the season to speed up the process.

Getting the markings right

After the chalk has settled, it's time for the marker lines to be drawn. This is precision work - nobody wants to mess up, because once the lines are in, a few centimetres of ice is built up on top once again, making any amendments or changes a pain in the...backside.

Drawing the hockey lines can take an entire day's work, before several more layers of water are added. Overall, the team spends two weeks preparing the rink. Then it's ready for action!

Now that people are skating regularly on the rink, the ice master uses slightly warm water to fix holes and repair the upper layer. Warm water does melt the ice minimally, but works better in repairing broken bits. It quickly freezes up anyway after. During each ride they distribute between 500-1,200 litres of water.

600,000 litres are needed to set up the entire rink - that's as much as leaving the tap running at home for three days.

The season ends in April, because the facility, constructed in the 1970s, is not suitable for year-round ice. Even in winter, the ventilation system is up and running all day, controlling the temperature in the hall. Maybe a new site in future could allow for figure skating and ice hockey in mid-July?