Myth: Glass marbles were used as ship ballast

Myths vs. Facts

By Kirsti Scott

sunken ship with ballast

Myth: Glass marbles were used as ship ballast

Fact: Rocks, sand, metal, and water were used as ballast

One of the persistent legends about glass marbles is that they were used as ballast on ships and ended up on beaches when ships sank or dumped their ballast. Unfortunately, this is 100% false.

Ballast is used to stabilize a ship in transit. Wooden sailing ships were extremely buoyant and the masts made them top-heavy. Ballast was added or removed from the hold at the bottom of the ship—depending on how much cargo, supplies, people, and weapons were on the ship—to make sure the ship stayed upright in heavy seas.

Once a ship got close to its destination, the ship would dump the ballast, often just outside the harbor. In fact, so much jettisoned ballast clogged the harbor at Ocracoke Inlet in North Carolina that they passed an act in 1784 requiring ships to dispose of their ballast prior to reaching the Cape Fear River channel.

The key was to transport ballast that could either be picked up and ditched at little to no cost, such as rocks, or could be sold when the ship came to port, such as heavyweight goods like china and pottery.

As soon as vessels started being made from metal, captains began using water as ballast. In 1776, we have the first documented example of a submarine using a ballast tank. In 1849, Abraham Lincoln, then an attorney from Illinois, patented a ballast tank system for cargo ships traveling on North American rivers. Later, steam-powered ships with metal hulls were able to carry water for the steam machine, and also for ballast. Water is perfect ballast, as it is always available and free.

marble factory

Now, back to glass marbles. The first automated glass-marble-manufacturing machine was invented by Martin F. Christensen of Akron, Ohio, in 1902. Before that time, glass marbles were made one at a time, by hand. There would be no reason for a ship to purchase handmade (or even machine-made) marbles, sea glass marbles


Where do the glass marbles come from that we find on the beach? There are two main sources: toys and manufacturing. If you find a colorful or swirly glass marble on the beach, it was used as a toy, and ended up on the beach either by being lost there or by eroding out of a town dump along the water. A larger glass marble in a light green color with a rough surface is likely an industrial marble, used in the manufacture of fiberglass, in a spray paint can, or as a reflector on an antique road sign. 

In any case, while glass sea marbles might not have crossed oceans before landing on your beach, they’re still a treasured find.

This article appeared in the Beachcombing Magazine September/October 2022 issue.

1 comment

A friend of mine picks up many sea marbles on a private beach with a sewage outlet

Ade January 21, 2024

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