Bullaugen

Bullaugen is the German term for portholes, circular windows set into the hull or bulkheads of a vessel. They provide natural light to interior spaces and, depending on design, ventilation while preserving watertight integrity.

Most Bullaugen are circular because this shape distributes pressure evenly and minimizes stress concentrations when a ship is subjected to waves and heel. They are typically fitted with a metal frame—made from brass, bronze, steel, or aluminum—and a pane of glass, often tempered or laminated. Some are fixed, while others are operable, with hinges or sliding mechanisms and gaskets to seal against water. Sizes vary widely, from small 10–15 cm examples on older ships to 30–60 cm on later hulls.

Historically, circular portholes were adopted in the 19th century as steel ships grew larger and the need for light in below-deck spaces increased. Advances in glazing and frame materials improved strength and watertight performance. In modern vessels, Bullaugen are commonly found in crew quarters, galleys, and other below-deck spaces; some configurations allow ventilation when the ship is in harbor or at anchor.

Safety and regulatory considerations emphasize watertight sealing and secure locking mechanisms. The term Bullauge is used in German maritime contexts, with the English equivalents being porthole or portlight.