Are Candle Clocks Very Accurate?

Are candle clocks very accurate? Candle clocks, an ancient timekeeping method, used a burning candle with marked intervals to measure time. Originating from an unknown source, the earliest reference is in a Chinese poem by You Jiangu in AD 520. The most sophisticated candle clock was created by Al-Jazari in 1206. The accuracy of these clocks depended on the quality of the candle and the conditions in which it was burned. Despite their innovative design, they were not as precise as modern timekeeping devices due to factors such as wind, temperature, and the quality of the wax.

Introduction

Candle clocks are an ancient time-keeping method involving a thin candle with consistently spaced markings. As the candle burns, it indicates the passage of periods. While they are no longer in use today, candle clocks were an effective way to tell time indoors, at night, or on a cloudy day. We find out if candle clocks are very accurate or not. 

History of Candle Clocks

The origins of candle clocks are unknown, but the earliest reference to their use is in a Chinese poem by You Jiangu in AD 520. You Jiangu’s device consisted of six candles made from 72 pennyweights (24 grains each) of wax, each being 12 inches high, of uniform thickness, and divided into 12 sections each of one inch. Each candle burned away completely in four hours, making each marking 20 minutes. The candles were placed for protection inside cases made of a wooden frame with transparent horn panels on the sides.

In medieval times, 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. Alfred used six candles, each made from 12 pennyweights of wax, and made to be 12 inches (30 cm) high and of a uniform thickness. The candles were marked at intervals of an inch. Once lit, they were protected from the wind by being placed in a lantern made of wood and a transparent horn. It would have taken 20 minutes to burn down to the next mark; the candles, burning one after the other, lasted for 24 hours.

The Most Sophisticated Candle Clock

The most sophisticated candle clock known to date was that of Al-Jazari in 1206. It included a dial to display the time and, for the first time, employed a bayonet fitting, a fastening mechanism still used in modern times. The candle, whose rate of burning was known, bore against the underside of the cap, and its wick passed through the hole. Wax collected in the indentation and could be removed periodically so that it did not interfere with steady burning. The bottom of the candle rested in a shallow dish that had a ring on its side connected through pulleys to a counterweight. As the candle burned away, the weight pushed it upward at a constant speed. The automata were operated from the dish at the bottom of the candle.

Are Candle Clocks Accurate?

The accuracy of candle clocks depends on several factors, including the quality of the candle and the conditions in which it is burned. The candles used in these clocks were made of uniform thickness and marked at consistent intervals. The rate of burning was known, and the candle was pushed upward at a constant speed as it burned away. However, factors such as wind, temperature, and the wax’s quality could affect the candle’s burning rate, potentially leading to inaccuracies in timekeeping.

In conclusion, while candle clocks provided an innovative way to measure time in the past, their accuracy depended on various factors and was not as precise as modern timekeeping devices.