Marbles have been used for games and industrial tasks since the ancient Romans and Egyptians began making them out of stone, clay, and marble. Modern day marbles are made of glass. Durable, inexpensive, and beautiful – glass checks all the boxes. Maybe they should be called “glassles”… but that’s beside the point.

Read More: Glass Fabrication Explained

In this video, Science Channel’s How It’s Made goes behind the scenes to find out how one company is making marbles out of recycled glass.

In the video above, recycled glass and defective marbles are thrown into a kiln heated to 1204 degrees Celsius for 16 hours to form a colorful mixture of molten glass. While draining the molten glass, a shearing device below the kiln cuts the stream of molten every half second, forming segments, called slugs, that become marbles. To make different size marbles, the device can be adjusted to cut at different intervals.

The slugs then need to cool for 72 hours between grooves on cast iron rolls that are spinning to keep the slugs from sticking.

The marbles are then funneled into channels that weed out marbles of the wrong size and collect the ones that are perfect.

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