Will a Piece Of Glass Sink or Float In Water?

I was at a dinner party the other night and a small group of friends was doing the dishes. We heard a smash of glass and pieces of the glass had fallen into the sink. Some friends had jokingly commented that the glass would float. Maybe you may have the same question, does broken glass float in water?

Broken glass will not float in water as it is too dense and does not contain enough air to float. Very small thin pieces of glass may float temporarily but this is only due to surface tension.

I will go into further details below on why glass will not float in water and explain a few myths that I hear about.

Does glass float in water

Will Glass Float in Sink Water?

Broken glass will not float in water unless it can trap enough air to keep it buoyant. Glass has a greater density than water and therefore cannot float on its own without a shape change.

Even laying a large sheet of glass gently on the surface of the water will not mean it can float. Glass is too dense……full stop!

What Is The Density of Glass and Why Doesn’t it Float?

Regular glass has a density of 2,500kg/m³ while water only has a density of 1,000kg/m³. This means that glass will always sink in tap water.

To drop the density of a glass bottle, you need to trap a pocket of air inside. If you put a cap on a glass bottle, it will now float!

This is the same reason why boats are able to float. They can trap pockets of air which enables them to float.

Does Broken Glass Float In Beer?

Broken glass will not float in beer as it is not dense enough. Beer does not contain enough solids to allow it to float.

A piece of broken glass would need to have such a shape to trap a pocket of air to allow it to float. This is highly unlikely within the small confines of a beer bottle.

Does a Glass Marble Sink or Float?

Glass marbles do not float as they have a greater density than that of most liquids including water.

A glass marble would need to be filled with enough air to offset its density in order for it to float.

Photo of author
Derrick Thompson
I have spent many years as a glazier working with glass and mirrors and this medium never ceases to amaze me. I decided to start this website to help share what I have learned and hopefully educate people about these wonderful building materials.

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