How glass marbles are made

A machine-made marble is rounded between two turning screws while it cools.

stations: 5
things upstream: 16
raw sources: 10
steps from the ground: 5

The short version

Machine-made glass marbles start as globules of molten glass dropped into a groove between two interlocking parallel screws. As the screws turn, the marble rolls along and is shaped into a sphere while it cools. Color comes from extra streams of colored glass blended into the main stream before the globule is cut.

Melt the glass

The base glass is a clear soda-lime batch of sand, soda ash and limestone melted in a furnace.

Goes in
Silica sand Soda ash Limestone
Stream in the color

Color is added to the main batch glass and to extra glass streams that merge with the main stream in different ways. In the cat's-eye style, colored glass veins are injected into a clear stream. Colored glass may also be applied to the surface of cheaper clear or white glass.
Drop globules into the groove

Blades chop the stream into globules, and each globule falls into a groove made by two interlocking parallel screws.
Roll it round between screws

As the screws rotate, the marble travels along them. It is gradually shaped into a sphere as it cools.
Cool and sort

The cooled marbles are sorted for size and flaws and bagged. Sizes usually range from about 0.5 to 3.5 cm across.

End of the lineGlass marble

Worth repeating

Vacor de Mexico makes 90 percent of the world's marbles, over 12 million a day.
In 1903, Martin Frederick Christensen of Akron, Ohio, made the first machine-made glass marbles on his patented machine.
A German glassblower invented marble scissors, a device for making marbles, in 1846.