Candle clock

Lore & Background

The earliest reference to candle clocks appears in a Chinese poem by You Jiangu (AD 520). His device consisted of six candles made from 72 pennyweights of wax, each 12 inches high, of uniform thickness, and divided into 12 sections of one inch. Each candle burned completely in four hours, making each marking 20 minutes. The candles were placed inside cases made of a wooden frame with transparent horn panels for protection. Similar candles were used in Japan until the early 10th century.

In medieval Europe, similar methods of measuring time were used in churches. The invention of the candle clock was attributed by the Anglo-Saxons to Alfred the Great, king of Wessex, as narrated by Asser, who lived at Alfred's court. Alfred used six candles, each made from 12 pennyweights of wax, 12 inches high, and of uniform thickness, marked at intervals of an inch. They were protected from wind by a lantern of wood and transparent horn, and the candles, burning one after another, lasted 24 hours.

Al-Jazari described a candle clock in 1206 that included a dial to display the time and, for the first time, employed a bayonet fitting. The candle bore against the underside of a cap, with its wick passing through a hole. Wax collected in an indentation and was removed periodically. The bottom of the candle rested in a shallow dish connected through pulleys to a counterweight, which pushed the candle upward at a constant speed as it burned.

Reader's Guide

Candle clocks represent an early and practical solution for measuring time in environments where sundials were ineffective, such as indoors, at night, or on cloudy days. The earliest known reference, from a Chinese poem of AD 520, shows that the basic design—a uniformly thick candle with inch markings—was already established. The device's use in Japan until the early 10th century indicates its spread across East Asia. In medieval Europe, the attribution of the candle clock to Alfred the Great by the Anglo-Saxons, as recorded by Asser, highlights its cultural significance, though the actual origin remains unknown. Al-Jazari's 1206 description marks a technological advance: his clock incorporated a dial for direct time reading and a bayonet fitting, a fastening mechanism still used today. The use of a counterweight and pulleys to maintain constant burning speed shows an understanding of mechanical regulation. Though no longer in use, candle clocks illustrate an important step in the history of timekeeping, bridging simple observation of burning rates with early mechanical innovation.

Did You Know?

• The earliest reference to a candle clock is in a Chinese poem by You Jiangu from AD 520.
• Alfred the Great's candles, each made from 12 pennyweights of wax, lasted 24 hours when burned one after another.
• Al-Jazari's 1206 candle clock was the first to employ a bayonet fitting, a mechanism still used today.
• Candle clocks were protected from wind by lanterns made of wood and transparent horn.