Deck Prism

deck prism

A deck prism (sometimes called a deadlight) is a prism inserted into the deck of a ship to provide light down below. For centuries, sailing ships used deck prisms to provide a safe source of natural sunlight to illuminate areas below decks Before electricity, light below a vessel’s deck was provided by candles, oil and kerosene lamps – all dangerous aboard a wooden ship. The deck prism was a clever solution: laid flush into the deck, the glass prism refracted and dispersed natural light into the space below from a small deck opening without weakening the planks or becoming a fire hazard.

In normal usage, the prism hangs below the ceiling and disperses the light sideways; the top is flat and installed flush with the deck, becoming part of the deck. A plain flat glass would just form a single bright spot below– not very useful general illumination– hence the prismatic shape. On colliers (coal ships), prisms were also used to keep check on the cargo hold; light from a fire would be collected by the prism and be made visible on the deck even in daylight.

One Trackback to “Deck Prism”

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.