Who knew watching and listening to a bartender chop block of ice into translucent jewels with a santoku knife could be so satisfying?

A Tokyo bartender recently got his five minutes of online fame after a video of him carefully turning blocks of ice into beautiful jewels went viral on Twitter, getting over one million views. It doesn’t sound like anything remotely interesting, but I spent close to an hour today just watching him slice the ice into almost perfects cubes and then cut the corners and sharp edges to create these crystal-like cubes for his patrons.

But it turns out that the bartender of Tokyo’s Bar Pralinka isn’t the only one who practices this satisfying art. Apparently, Japan has a long tradition of hand-carving ice cubes using extremely sharp knives to slice through the hard ice. But there is more to these beauties than knives, a firm hand and patience. You also need the right kind of water.

To get that kind of crystal-like clarity, you need to first filter the water, sometimes several times, making sure it’s completely free of impurities. Then using the heavy blade of a santoku or Deba sashimi knife, you slice the chunks of ice into smaller pieces and then into cubes.

Although the jewel design is the most common, some masters of ice-cube sculpting take it to the extreme, cutting smaller facets into the cube at angles until they create a spherical shape. Then they hack at any imperfections to make a perfect sphere.

Hand-carving ice cubes is not that common in Western bars, although there are companies that specialize in creating bespoke ice-cubes by using chainsaws and bandsaws.